natural and cultural landscape evolution during the … · natural and cultural landscape evolution...
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Natural and cultural landscape evolution during
the Late Holocene in North Central Guatemalan
Lowlands and Highlands
Carlos Enrique Avendaño Mendoza
A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy
Graduate Department of Geography University of Toronto
© Copyright by Carlos Enrique Avendaño Mendoza, 2012
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Natural and cultural landscape evolution during the Late Holocene in North Central Guatemalan
Lowlands and Highlands
Doctor of Philosophy 2012
Carlos Enrique Avendaño Mendoza Graduate Department of Geography
University of Toronto
Abstract Paleoecology has been only in recent decades applied to Mesoamerica; this thesis
provides new records of paleoenvironmental changes in Guatemala. Paleoecological
reconstructions are developed based mainly on pollen in the Lachuá lowlands and
Purulhá highlands of the Las Verapaces Region. For the first time, quantitative vegetation
and climate analyses are developed, and plant indicator taxa from vegetation belts are
identified. Changes in vegetation are explained partially by elevation and climatic
parameters, topography, drainage divides, and biogeography. Pollen rain and indicator
plant taxa from vegetation belts were linked through a first modern pollen rain analysis
based on bryophyte polsters and surface sediments. The latter contain fewer forest-
interior plant taxa in both locations, and in the highlands, they contain higher local pollen
content than in the lowlands. These calibrations aided vegetation reconstructions based
on fossil pollen in sediment records from the Lachuá and Purulhá regions.
Reconstructions for the last ~2000 years before present (BP) were developed based on
fossil pollen from cores P-4 on a floodplain in Purulhá, and L-3, a wetland in Lachuá.
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Core P-4 suggests that Mayan populations developed a system of agricultural terraces in
a former paleolake-swamp environment, which was abandoned at the time of the Spanish
Conquest (~400 BP). Core L-3 indicates the abandonment of Mayan “Forest Gardens” at
the time of the early Postclassic. These gardens likely prevailed during the Classic period
(~300-1100 yrs BP) at the outskirts of the ancient city of Salinas de los Nueve Cerros.
Following abandonment, forest recovery took place for about 800 yrs. Cultural factors are
found to be more important in determining vegetation dynamics in this region, since no
clear evidence of climate forcing was found. The P-4 and L-3 cores provide likely
evidence that Mayan populations were, contrary to other evidence, innovative landscape
managers. Scenarios in the Las Verapaces Region have been drastically modified in
recent times (e.g. after the European Conquest), as suggested by pollen evidence in the
top of both P-4 and L-3 cores, possibly due mostly to modern large scale natural
resources exploitation, which represent environmental threats greater than any seen in the
last ca. 2000 years.
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Acknowledgments
I deeply thank my supervisor Sharon Cowling for her sincere and wonderful support
during the development of my Ph.D since the very first day I arrived to Canada. She was
there waiting for me in the Toronto International Pearson Airport with a sign that had my
name on, I can only say “Muchas gracias eternas”. Thanked is my co-supervisor Sarah
Finkelstein for her marvellous support at the Paleoecology Laboratory of the Department
of Geography. I had the honor to be at the start of her Laboratory and see the evolution to
what today is: An excellent place to learn and grow.
I thank Prof. Tenley Conway and Prof. Anthony Davis for their helpful comments as part
of my Ph.D. Academic Committee. Prof. Juan Carlos Berrio is greatly thanked for his
valuable training in tropical paleoecology during field campaign in Guatemala and during
my visits to his laboratory at the Department of Geography, Leicester University,
England. I thank his wife Natalia de Berrio for her support too. I thank too the “Los
Juanetes”, a Latin American rock band in the middle of England, for making my visit a
nice one. I thank the Guatemalan team, “los COMPAI” and more, that supported me
during my field campaign in Guatemala in 2006 and many many more things.
Lachuá National Park and Biotopo del Quetzal Administrations and staff are thanked for
supporting my research. I am greatly thankful to forest guards at Lachuá National Park
for their support in bryophyte polster and core sampling. I thank Santa Lucia Lachuá
Municipality for support in collecting sediments from Salinas de los Nueve Cerros,
especially to Major Pedro Oxom and Family Tun. San Cristobal Verapaz Municipality
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Administration and staff are thanked for supporting our research. Fincas Villa Trinidad,
Patal, Chisiguan, and Lesbia Mus and Yolanda Barahona are thanked for their support in
collecting sediments.
I thank CONAP, Franklin Herrera, Escuela de Biología –at the Faculty of CCQQ and
Pharmacy –USAC- for the support in acquiring collection and research licenses. As well
I thank staff and members of Escuela de Biología, Faculty of CCQQ and Pharmacy, and
USAC for their support during my Ph.D.
I thank Dr. Gerald Islebe for his support in pollen identification and feedback during my
thesis development. Enric Aguilar and Melissa Gervais are thanked for obtaining
Guatemalan climatic information. Joan Bunbury is greatly thanked for the support in
creating maps and using CANOCO ©. Dr. Arnoud Boom is thanked for his support
during my visit to Leicester University, England (as well, thanks for introducing me more
into Asian Cinema). Grace Jeon is thanked for her support in developing Loss-on-ignition
measurements for my core samples in the Paleoecology Lab, Department of Geography –
UofT-. The Centre for Global Change Science and their staff, especially Ana Sousa, at
the University of Toronto is greatly thanked for enhancing my Ph.D. experience. I thank
Prof. Jock McAndrews and Charlie Turton for their support during my Ph.D.
I thank everybody at the Department of Geography who supported me during my Ph.D.
years as a student, especially from the main office at Sidney Smith (esp. Marianne
Ishibashi, Marika Maslej, and Jessica Finlayson). I am very grateful to the Physical
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Geography Building (PGB) community who supported and helped me, especially
members of Cowling and Finkelstein’s research laboratories. Members of Chen’s,
Diamond’s and Desloge’s laboratories are greatly thanked for their company and support.
I am greatly grateful to Mircea Pilaf for his support since the first day I arrived to PGB
and for the conversations in Romanian. I thank the “Geography soccer” community
whom I shared many summer, fall, winter, and spring games. Thanked are Maria Johnson
and Family for being my Guatemalan-“Chapina”-Canadian Family.
I am grateful to Claudia Avendaño and Knutt Eissermann for providing help and time in
finding the source vegetation literature for this study. I am grateful to Maria Elena
Hidalgo “mi Ague”, Carlos Avendaño E., Yolanda Mendoza de Avendaño, Gary
Avendaño, and Hector Bol for providing help during field work. I thank my Family in
Guatemala for their spiritual and moral support: Papa, Mama, Clada, Gary, Abue, Hector,
Ti Lili, Dn. Enrique, Kennes ... This thesis is dedicated to my Family, which has
supported me in my entire life in any possible path that I have taken … forever and ever.
Special dedication for Mateo and Belinda, who now have become my triangle of life, joy,
and motivation to become a better being. Mateo:
“No llegó la gota carmín, Llegó en su lugar la noticia de su visita, Certidumbres y rumbos no aleatorios, A esta edad, en este lugar, en esta vida… Semilla liberando indicios de luz, Transformando auras, metamorfosis interna, Milagro de la multiplicación de tu rostro en cada rostro, en el niño de la calle, en el abuelo de la esquina, en el rostro del espejo, Bien leí que en tradiciones ancestrales se entiende como la llegada de un maestro, En silencio quiero aprender de ti… Después de años de ser profecía, la epifanía llego esta mañana: reconocer al prójimo como a mi propio hijo… Traes polvo cósmico celestial, soplas tu aliento en mi oído y me revelas el universo”.
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Table of Contents Abstract ............................................................................................................................... ii
Acknowledgments...................................................................................................... iv List of Tables ............................................................................................................. ix List of Figures ............................................................................................................. x List of Appendices .................................................................................................... xii
Chapter 1: Background Information ................................................................................... 1 1.1 Pollen as a Paleoecological Proxy ........................................................................ 1 1.2 Climate Variability Over the Holocene ................................................................ 4 1.3 Reconstructing vegetation and landscapes............................................................ 8 1.4 Reconstructing Cultural Landscapes................................................................... 10 1.5 Thesis Objectives and Research Questions......................................................... 13 1.6 Geomorphological and Vegetational Setting of Study Region........................... 15 1.7 Cultural History of Study Region ....................................................................... 20
Chapter 2 Vegetation Distribution along the Las Verapaces region in North Central Guatemala.... 27
2.1 Introduction......................................................................................................... 27 2.2 Methods............................................................................................................... 30 2.3 Results................................................................................................................. 35 2.4 Discussion ........................................................................................................... 47 2.5. Chapter summary ............................................................................................... 54
Chapter 3 Modern pollen rain in the north-central Guatemalan lowlands and highlands................. 56
3.1 Introduction......................................................................................................... 56 3.2 Methods............................................................................................................... 59 3.3 Results................................................................................................................. 64 3.4 Discussion ........................................................................................................... 85 3.5. Chapter summary ............................................................................................... 95
Chapter 4 Late-Holocene History of a Highland Floodplain in Las Verapaces, Guatemala............. 98
4.1 Introduction......................................................................................................... 98 4.2 Methods............................................................................................................... 99 4.3 Results............................................................................................................... 103 4.4 Discussion ......................................................................................................... 115
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4.5. Chapter Summary ............................................................................................ 132 Chapter 5 The Lachuá Lowlands Rain Forest in Guatemala: 2,000 yrs of forested landscape? ..... 134
5.1 Introduction....................................................................................................... 134 5.2 Methods............................................................................................................. 136 5.3 Results............................................................................................................... 139 5.4 Discussion ......................................................................................................... 149 5.5 Chapter summary .............................................................................................. 161
Chapter 6 Conclusions..................................................................................................................... 163
6.1 What are the factors that explain vegetation distribution along the Las Verapaces environmental gradient and what taxa can be used as "indicator species"? ........... 164 6.2 Can paleoecological calibrations for fossil pollen be constructed from a comparison of modern pollen rain from surface sediments and bryophyte polsters?................................................................................................................................. 166 6.3 What are the major vegetation changes recorded in the highland core from the Las Verapaces region? ............................................................................................ 168 6.4 What are the major vegetation changes recorded in the lowland core from the Las Verapaces region? ............................................................................................ 170 6.5 What is the role of natural variability and cultural factors related to the Maya Civilization in the evolution of landscapes in the Las Verapaces Region? ............ 172
References....................................................................................................................... 174 Appendices...................................................................................................................... 196
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List of Tables
Table 2.1. Sites included in the Las Verapaces Gradient, providing a total of 23 sampling units (SU) from 9 sites spanning an elevation gradient of 170 to 2532 m asl. Table 2.2. Indicator plant taxa for the three vegetation belts along the Las Verapaces Gradient, selected from DCA axis scores for species (see text for details). Table 2.3. Generalist plant taxa for the Las Verapaces Gradient, as determined by DCA axis scores for species (see text for details). Table 2.4. Disjunctive plant taxa distributed in Lowland Rain Forest and Montane Cloud Forest in the Las Verapaces Gradient generated from DCA axis scores for species (see text for details). Table 3.1. Pollen types and their % range for bryophyte polsters and surface sediments. Information about vegetation belt, plant habit, and pollen dispersal syndrome is provided. Table 3.2. Lachuá bryophyte polsters and surface sediments samples. Table 3.3. Purulhá bryophyte polsters and surface sediments samples. Table 3.4. Factor Analysis scores for pollen types with highest amount of variance. Table 4.1. P-4 core stratigraphic sequence. Table 4.2. Radiocarbon dates, calibrated age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá Table 5.1. Radiocarbon dates, calibrated age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá.
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List of Figures
Figure 1.1. Temperature changes in the late Pleistocene and the Holocene inferred from oxygen-18 measurements in Greenland ice core (taken from Dergachev and van Geel, 2004). Figure 1.2. Location of Guatemala in Central America. Numbers indicate location of meteorological stations. Figure 1.3. Topographic map of the Las Verapaces Region in Guatemala. Figure 1.4. Topographic map of study sites in the Las Verapaces Region in Guatemala. Map I= Lachuá lowlands, Map II= Purulhá highlands. Figure 2.1. Detrended Correspondence Analysis diagram of Las Verapaces sites along the first two DCA axes. Figure 2.2. Linear regression of Detrended Correspondence Analysis (DCA) Axis 1 scores (raw scores) of indicator plant taxa (A) and sites (B) against elevation values per site of the Las Verapaces Gradient. Figure 2.3. Linear regression curves for temperature (°C) from meteorological stations from Central and Northern Guatemala. Figure 2.4. Detrended Correspondence Analysis diagram for the Las Verapaces Gradient sites and climatic variables. Figure 2.5. A) Indicator (in one vegetation belt) and B) generalist (across two vegetation belts) taxa separated according to their biogeographic origin along the Las Verapaces gradient vegetation belts Figure 3.1. Location of Guatemala in Central America. Las Verapaces Region is enclosed in rectangle. Figure 3.2. Pollen diagram from Lachuá and Purulhá based on bryophyte polsters and surface sediment samples. Figure 3.3. Lachuá pollen diagram based on bryophyte polsters and surface sediment samples. Figure 3.4. Lachuá DCA Q-mode diagrams of arboreal pollen data with Pinus removal. Figure 3.5. Purulhá pollen diagram based on bryophyte polster and surface sediment samples.
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Figure 3.6. Purulhá DCA Q-mode diagrams based on arboreal pollen and non-arboreal pollen data. Figure 3.7. Las Verapaces DCA Q-mode diagram AP shared data. Figure 4.1. P-4 core paleoecological diagram taken from Cahabón River Flooplain. Figure 4.2. Graph showing depth (cm) vs. calendar age (cal yrs BP) of sediments from core P-4 taken from the Cahabón River floodplain. Figure 4.3. Principal Component Analysis (PCA) of sampled levels from core P-4. Figure 4.4. Pollen percentage diagram of P-4 core from the Cahabón River floodplain. Figure 4.5. Location of the headwaters of the Cahabón River and the floodplain. Figure 4.6. Principal Component Analysis (PCA) of modern pollen rain samples from Purulhá highlands and fossil samples from core P-4. Figure 4.7. Principal Component Analysis (PCA) of modern pollen rain samples from Purulhá highlands and sampled levels from core P-4. Figure 4.8. Cahabón River and its floodplain. Series of 3 arrows indicate river flow direction. N= North, masl=meters above sea level. Taken by J.C. Berrio © 2006. Figure 5.1. L-3 core paleoecological diagram taken from a wetland next to Lake Lachuá. Figure 5.2. Principal Component Analysis (PCA) of sampled levels from core L-3. Figure 5.3. Pollen percentage diagram of L-3 core from a wetland next to Lake Lachuá. Figure 5.4. Location of the ancient Mayan city of Salinas de los Nueve Cerros on the banks of the Chixoy River, Alta Verapaz, Guatemala. Figure 5.5. Principal Component Analysis (PCA) of modern pollen rain samples from Lachuá lowlands and fossil samples from core L-3.
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List of Appendices
Appendix 2.1. Indicator, generalist, and disjunctive plant checklist. Appendix 3.1. Pollen types found in modern pollen calibrations and fossil pollen spectra from cores P-4 and L-3. Associated plant and uses by ancient Mayan populations are shown. Appendix 4.1. Pollen counts (raw) from P-4 core. Appendix 5.1. Pollen counts (raw) from L-3 core.
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Chapter 1: Background Information
1.1 Pollen as a Paleoecological Proxy
One of the main objectives of paleoecological research is to reconstruct environmental
changes occuring at different scales of resolution, from global to local scales (Bennington
et al., 2009; Birks, 2005; Hunter, 1998; Willis and Birks, 2006). Many Holocene
examples can be cited that demonstrate how natural and cultural factors influence the
evolution of landscapes and regions (Berrio et al., 2001; Lorimer, 2001; Muñoz and
Gajewski, 2010; Ye et al., 2010). The likely reason for the emphasis on separating natural
from cultural factors relates to our understanding of whether current global
environmental trends are due to natural variability, cultural factors, or some combination
(Harris, 2003; Cao et al., 2010).
Vegetation is a fundamental component of ecosystems, landscapes and regions, and has
been used widely as a paleoecological indicator (Markgraf et al., 2009; Valsecchi et al.,
2010; Cheng, 2011). Vegetation was chosen as a proxy for landscape evolution because
of its intimate relationship with climatic and topographic variability (Clark, 2007;
Davidar et al., 2005; Simona et al., 2009). Vegetation reflects the environmental and/or
cultural regimes that control landscapes and regions at different spatio-temporal ranges.
The chosen proxy for vegetation reconstruction is pollen because of its taxonomic
specificity and because it reflects processes related to vegetation dynamics (i.e.
pollination), in addition to the fact that it has been studied thoroughly and used often for
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different applications in biogeography, climate change, biome reconstructions, and
archaeology (Berrio et al., 2001; Birks and Birks, 2003.; Graham, 2006; Marchant et al.,
2009). The relationship between vegetation and pollen found in depository records, either
superficial or sedimentary, is not 1:1 because of the multiple factors that are involved in
pollen release, transportation, deposition and preservation (Brown et al., 2007; Bunting et
al., 2004; Campbell, 1999; Fægri and Iversen, 1989). It is necessary to understand the
relationship between vegetation and pollen collected from depositories, in order to
understand pollen representation at modern or past times for a determined landscape and
region. Therefore the concept of uniformitarism underlies palynological research: it is
assumed that the chosen proxy has had a response in the past similar to its responses to
present-day natural and cultural changes (Bradley, 1999).
Vegetation has been closely linked to human history and activities (e.g. agriculture and
forestry) because vegetation provides a resource source for multiple needs: timber,
fuelwood, medicine, food, and resins (Fuller et al., 2010; Innes et al., 2009; Rokaya et al.,
2010; Weiser and Lepofsky, 2009). Complementary use of archaeological methods helps
to broaden our ability to understand human impact on landscapes (Li et al., 2010; McKey
et al., 2010; Weiss and Brunner, 2010). Pollen grains (i.e. as micro-botanical remains or
microfossils) have been widely used in paleoecology and have become relevant proxies
to reveal natural and cultural factors in landscape evolution (Lozano-García et al., 2010;
Scharf, 2010). Changes in pollen composition, pollen abundance, and information related
to the presence or absence of specific taxa provide the foundation for paleoecological
reconstructions of past environmental change.
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Modern pollen spectra have been studied from bryophyte polsters (e.g. mosses and
liverworts) and are collected mostly from the interior of non-disturbed forests
(Domínguez-Vázquez et al., 2004). These studies are important in understanding the
conditions under which the pollen is deposited; these studies are also necessary for
comparisons (i.e. in presence, absence and abundance) between observed pollen signal
and surrounding plant taxa. This modern-day calibration process is necessary for the best
possible interpretation of the fossil pollen record.
Topography affects energy distribution in landscapes, such as water and wind flows
where pollen transportation occurs (Schueler and Schluenzen, 2006; Vogler et al., 2009).
The role of topography in affecting pollen transport, however, is not entirely understood
(Higgins et al., 2003). These processes have mostly studied with respect to maize pollen
in terms of cross-pollination in agricultural fields (Klein et al., 2003). On its own,
elevation above sea level has an influence on pollen dispersal and deposition because of
orographic effects related to patterns of wind circulation (Fægri and Iversen, 1989).
Regionally-dispersed pollen is sensitive to atmospheric conditions, for example, because
surface convection (i.e. air turbulence from heating) can raise pollen above the canopy-
level, causing long-distance, horizontal transfer until the air parcel eventually cools and
descends (Murray et al., 2007), or it encounters a “disturbance” in flow such as a lake
basin causing pollen to fall out of the atmosphere (Sugita 1993). Provenance of pollen
may also be a source of bias in interpreting paleoecological signals because where
sediment is deposited (i.e. lakes, rivers, oceans) and how it is transported (i.e. by wind,
water, terrestrial and aquatic animals) is important (Traverse, 1994; Nielsen, 2005). Once
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pollen grains land on a surface, they will respond to the physical, chemical, and
biological processes occurring on the surface, that in turn determine sedimentation and
preservation of pollen samples. The understanding of taphonomy and pollen-environment
relationship is determinant in pollen analysis, since an important assumption is that the
pollen assemblage recorded from a sediment sample is the same as the originally
deposited (Twiddle and Bunting, 2010).
The wide ranging applications of pollen analysis in paleoecology have increased the
research scope to conservation biology and biogeography. For example, conservation
efforts have been directed where plant communities in riparian environments have been
identified as relicts (i.e. early Holocene), after studying pollen spectra in sedimentary
records found in floodplains (Southgate, 2010). At the geological scale, pollen records
have been the basis to explain the evolution of biomes coupled to tectonic processes (e.g.
orogeny) based on pollen spectra collected in lakes sediments in the Andes
(Hooghiemstra et al., 2006).
1.2 Climate Variability Over the Holocene
Reconstucting past climate changes is important for explaining roles of external and
internal forcings on the climate system and for predicting future trends. External forcings
on the climate system include changes in orbital parameters of the Earth, and solar
variability; internal forcings, by contrast, are related to processes that occur within the
Earth system (e.g. volcanic activity) (Beniston, 2005). The Milankovitch Cycles are
important variations in Earth’s orbit, known mostly for their role in promoting the
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Pleistocene Ice Ages (Lisiecki, 2010). The parameter of eccentricity (the measure of the
shape of the Earth's orbit around the sun) varies on a timescale of ~ 100,000 yrs and
contributes to glacial-interglacial cycling (Berger, 1989). The other two Milankovitch
parameters are: obliquity (measure of the Earth’s rotation tilt from 22 to 24.8° every 41
ky) that is responsible for the definition of tropical and circum-polar latitudes, and
precession of the equinoxes (which cycles on a scale of 19 to 26 ky), which is related to
solar insolation variability as a function of the Earth-Sun distance at the moment of the
vernal equinox. The interaction of the three Milankovitch parameters is consistent with
recorded climatic variability at the multi-millenial timescale, by producing a complex
pattern of solar radiation reception on Earth’s atmosphere (Mendoza, 2005). Large-scale
biotic processes such as migration and colonization have been affected by these cycles
and modern day biogeography has been greatly influenced by the glacial – interglacial
cycling of the Quaternary (Erwin, 2009; Kerhoulas and Arbogast, 2010).
At a much smaller time scale, solar variability as evidenced through the sunspot cycles of
11, 22 and 240 years, result in changes in the amount of short wave radiation reaching the
Earth (Rapp, 2010). Decreased occurrence of sunspots is believed to be one of the factors
explaining reductions of global temperature (see Little Ice Age below) (Haase-Schramm
et al., 2005).
Internal forcing of climate is related to volcanic activity (i.e. tectonics), ocean circulation,
and critical changes in the biosphere (marine and terrestrial) and cryosphere (Beniston,
2005). Volcanic activity cools the climate because particulate matter emitted from the
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eruption changes the Earth's albedo, increasing solar energy reflectance. Ocean
circulation patterns affect the climate, such as the associated drop in global temperatures
due to a weakening of the thermohaline circulation during the Younger Dryas (ca. 11,000
yrs BP) and Little Ice Age (ca. 300 yrs BP) (Bradley and England, 2008; Helama et al.,
2009). Variability in other circulations could have more regional effects at decadal time
scales such as El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation
(NAO) (Seager et al., 2010). The former is associated to the contraction and expansion of
warm waters in the west Pacific, and the latter is believed to account for ca. 50% of
variability in sea level pressure on both sides of the Atlantic Ocean. The internal forcing
factors have in common that they operate at a sub-millenial time scale.
The explanation of the Holocene climatic variability requires understanding the coupled
effects of external and internal forcings. During the last 10,000-12,000 years the
Holocene stands as an epoch of warmth and steady climate, characterized by centennial
and millennial-scale alternating of cold and warm periods, superimposed over a long-
term trend of first warming and then cooling (Bjune et al., 2004). The onset of the
Holocene climate has been shaped by the cyclical transition from a glacial to an
interglacial where the maximum insolation was experienced (~10 ky BP) (Solanki et al.,
2004) (Figure 1.1.). Thereafter four warming maxima, alternated by cold stages, have
been deducted from paleoecological data during the intervals: 6700-5700, 4500-3200,
2300-1600, and during 1150-900 yrs BP (the Medieval Climatic Optimum) (Dergachev
and van Geel, 2004). Cold Heinrich events (stadials) and Dansgaard-Oeschger warm
stages (interstadials) are important factors that are believed to play a role determining
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climatic shifts at the millennial scale (Merkel et al., 2010). Millennial to centennial
natural variability modifies macro-regional climatic regimes and therefore more localized
dynamics such as forest humidity and temperature (Jouzel et al., 2007; Popescu et al.,
2010).
Although global climatic synchronicities have been recognized, regional variations play a
critical role in understanding biogeographical patterns found at smaller spatio-temporal
scales (Viau and Gajewski, 2009). Variability in the location of the Intertropical
Convergence Zone (Chiang and Bitz, 2005; Holbourn et al., 2010) and cyclicity of ENSO
(Merkel et al., 2010) are of major importance to understanding climatic variability at
more regional scales in Mesoamerica. Evidence of climatic variability in the Yucatán
Peninsula, is derived from the 206-year period oscillations of oxygen isotopes and
gypsum precipitation from Lake Chicancanab, and possibly related to variation in solar
radiation (Hodell et al., 2001). Similar paleoclimatic patterns have been gathered from
Figure 1.1 Temperature changes along the late Pleistocene and the Holocene inferred from oxygen-18 measurements in Greenland ice core (taken from Dergachev and van Geel, 2004).
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the Circum-Caribbean, Lake Valencia and the Cariaco Basin in Venezuela, and when
combined with the Chicancanab data, aligns with critical processes along major cultural
periods (Alley et al., 2003; Hodell et al., 1991; Peterson et al., 1991). Arid events have
been associated with cyclic events and include observed droughts between 150 and 250
AD (Pre-Classic abandonment), 750-1050 AD (Terminal Classic Collapse) and 1450 AD
(Post-Classic) (Hodell et al., 2007).
The climate system is currently understood as the product of the coupled interactions
between the atmosphere, hydrosphere, lithosphere, cryosphere, and biosphere.
Information provided by paleoclimatic studies provide scientific basis for hypothesis
testing of climatic variability in determined locations under different temporal scales of
resolution.
1.3 Reconstructing vegetation and landscapes
A large number of vegetation reconstructions based on pollen have been conducted
around the world, spanning time periods from hundred to millions of years ago, and have
provided important information to determine the roles of natural factors in landscape
evolution. Based on changes in pollen composition, it has been possible to identify a high
correlation between tectonic processes of the Andean orogeny of the last 3 million years
(Mya) with altitudinal changes in North Andean biomes (Hooghiemstra and Van der
Hammen, 2004; Torres et al., 2005). In coastal environments, sea level changes at the
multi-millenial scale have been analyzed based on regressive and transgressive phases
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reconstructed from sedimentary sequences, and have been used in conjunction with
pollen information to show an inland-to-coast migration of vegetation (Torrescano and
Islebe, 2006; Gabriel et al., 2009). Milankovitch cycles affect the retreat and advance of
glacial ice caps, events that can be recognized in pollen diagrams showing latitudinal tree
line oscillations (Kramer et al., 2010). Other periods of natural climatic variability such
as the Younger Dryas stadial (cold event) (Kokorowski et al., 2008) and solar cycles are
evident in pollen diagrams (Morner, 2010). Pollen from the Arctic specialist Dryas
octopetala is used as an indicator of the Younger Dryas because of the increase in
distribution and abundance of D. octopetala at this stadial (Joosten, 1995).
In places such as the Mexican Central Highlands and the Lacandon rain forest in Chiapas,
evidence of the Maya Terminal Classic (800-900 century AD) drought event has been
interpreted based on the increase of Pinus pollen (Almeida et al., 2005; Domínguez-
Vázquez and Islebe, 2008). In contrast, reconstructions from neighboring regions such as
the Mexican Sierra Madre Oriental (East-Central Mexico) (Conserva and Byrne, 2002)
and Sierra de Los Tuxtlas (Lozano-García et al., 2010) show no evidence of drought and
actually indicate slightly moister conditions. Geographical variability in precipitation
may be because of orographic effects in topographically complex regions, which creates
climatic envelopes at the regional scale. For example, Wendt (1989) proposed the
existence of a wet belt across the Gulf of Mexico, Southeast of Mexico, Central
Guatemala, and the Izabal province (Caribbean Guatemalan Coast), which possibly
allowed the permanence of hypothesized tropical rain forests pleistocenic refuges.
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Data from Los Tuxtlas show evidence of the Little Ice Age (LIA) in the Gulf of Mexico;
multi-proxy records indicate wetter conditions around 1500 to 1700 AD (e.g. increased
lake levels and increased accumulation rates of pollen of lowland or highland forest taxa)
(Lozano-García et al., 2007; Lozano-García et al., 2010). In contrast, reconstructions
based on oxygen isotopes and titanium content from the Yucatán peninsula (Aguada
X’caamal) and the Cariaco basin (respectively) show lower precipitation between 1500
and 1800 AD (Hodell et al., 2005). Climate proxies and the presence of Zea pollen from
Lake Tzib at Quintana Roo, Mexico (Carrillo-Bastos et al., 2010) likely indicate higher
precipitation around 1200 AD contrary to what would be expected during the time of the
Medieval Warm Period (MWP) (just before the LIA).
1.4 Reconstructing Cultural Landscapes
Pollen can also be used to reconstruct anthropogenic impacts on landscapes during
different cultural periods, for example, during the early Holocene phase of hunters-and-
gatherers (Kunes et al., 2008). Cultural impacts on the environment are of greater interest
for more recent times, including the transition from nomadic human populations to fully
sedentary communities (Rowley-Conwy, 2009). It is when human groups started to
remain in one area for longer periods of time that we can see a clear anthropogenic signal
in the paleo-record, reflecting the evolution of agriculture as an important modifier of
landscapes.
In different culturally important regions around the globe (the Near East, Ganges Delta,
Yellow River watershed), the origins and development of agriculture have been
11
reconstructed based on the first appearance of cereal pollen cultigens. In the case of
Mesoamerica, corn pollen (Zea mays L.) is traced (Zizumbo-Villarreal and Colunga-
García, 2010) whereas in China, the initial presence of rice pollen (Oryza sativa) is used
to signify the beginning of agriculture (Fuller et al., 2009). The reconstruction of
landscapes histories based on architectural and ceramic remains (i.e. archaeological
methods) is complemented with the use of pollen because it can tell a more complete
story about an area, including information on landscape management, levels of
disturbance, and conservation efforts (Bettis III et al., 2008; Dambrine et al., 2007;
Delhon et al., 2009; Mercuri, 2008).
The magnitude to which anthropogenic activities influence landscapes is a topic of much
discussion between researchers (Horrocks et al., 2007; Williams et al., 2010; Yu et al.,
2010; Zhao et al., 2010). Numerous scholarly theories have been derived depending on
the type of evidence collected (i.e. paleoecological versus archaeological) and the cultural
context in which that evidence is found. On the one hand, ancient cultures have been
considered responsible for major modifications to landscapes; involving activities that
generally bring upon detrimental societal consequences as a result of natural factors such
as soil erosion and resource depletion (Diamond, 2009; McWethy et al., 2009). It has
been suggested that anthropogenic activities (particularly changes in land-use) can alter
regional climate, such as precipitation (Shaw, 2003; Gill et al., 2007) and therefore could
play an interactive role in prolonging periods of drought and/or deepening the magnitude
of water stress. From this perspective, anthropogenic activities are considered the critical
trigger in the collapse of past societies (Diamond, 2005).
12
In contrast, past societies can be viewed from the perspective of practicing sustainability
of resources in their everyday activities, such as the planting of trees to prevent large-
scale erosion of highlands (Smith and Demarest, 2001; Aimers, 2007). From this second
point of view, the “collapse” of an ancient civilization has foundations in multi-factorial
processes, both anthropogenic and natural (e.g. biotic, abiotic) (Demarest et al., 2004;
Demarest, 2009).
Regardless of how human activity is viewed within ecosystem dynamics, evidence shows
an increasing effect of changes in greenhouse gas concentrations in the atmosphere, since
the onset of agricultural activities, the introduction of large-scale herding of grazers, and
most recently due to the burning of fossil fuels (Olofsson and Hickler, 2008; Brook,
2009). The "Anthropocene", a controversial naming of the latter period of the Holocene,
has been defined by the period of over-arching effects of humans on climatic, hydrologic
and edaphic cycles (Ruddiman, 2003; Crutzen, 2006).
13
1.5 Thesis Objectives and Research Questions
1.5.1. Rationale.
The role of natural and cultural factors in the evolution of landscapes within the Las
Verapaces region of north-central Guatemala is the focus of this thesis. Natural and
cultural factors can intermingle or act independently at different spatio-temporal scales
(Clark, 2007; Díaz and Stahle, 2007; Partel et al., 2007; Sarmiento et al., 2008;
Wainwright, 2008). The separation of past cultural and natural processes by using
paleoecological methodology is needed to help provide a solid scientific basis to assess
modern-day impacts of human activities at the global, regional and landscape scales. This
thesis is developed in the Lachuá lowlands and the Purulhá highlands of the Las
Verapaces region, an important location in the Mesoamerican context due to its high
biological and cultural diversity, which nevertheless lacks exploration in paleoecological
terms.
1.5.2. Approach.
My approach involves paleovegetation reconstructions of the Lachuá lowlands and the
Purulhá highlands in the Las Verapaces Region from the Preclassic to modern-day times,
covering the past two millennia. To develop paleo-vegetation reconstructions for the Las
Verapaces Region, it was necessary to first determine the taxonomic composition of
vegetation communities and the altitudinal distribution of vegetation types, including
explanations for their geographical variation (Chapter 2). Since the relationship between
the abundance of pollen grains and the abundance of corresponding vegetation is not 1:1,
14
it was necessary to develop the first calibration study of the region by comparing pollen
sources such as lake sediments and bryophyte polsters and analyzing the modern pollen
rain (Chapter 3). Paleoecological reconstructions were developed based on fossil pollen
spectra collected from a core (P-4) from the Cahabón River floodplain at the Purulhá
highlands spanning the last ~2390 years (Chapter 4) and a wetland core (L-3), taken
adjacent to Lachuá Lake, within the Lachuá lowlands (Chapter 5) spanning the last
~2000 years.
Research Questions. The main research questions addressed in this thesis include:
a) What are the factors that explain vegetation distribution along the Las Verapaces
environmental gradient and what taxa can be used as "indicators"?
b) Can paleoecological calibrations for fossil pollen be constructed from a
comparison of modern pollen rain from surface sediments and bryophyte polsters?
c) What are the major vegetation changes recorded in the two (lowland, highland)
cores from the Las Verapaces region?
d) What is the role of natural variability and cultural factors related to the Maya
Civilization in the evolution of landscapes in the Las Verapaces Region?
15
1.6 Geomorphological and Vegetational Setting of Study Region
The Las Verapaces region is located in north central Guatemala, encompassing sharp
environmental gradients from the Lachuá lowlands (~170 masl) to the Purulhá highlands
(~2500 masl) (Figure 1.2). In addition to being characterized by environmental gradients,
I also selected the region because of the absence of paleoecological research (Islebe and
Leyden, 2006) despite its importance in both natural and historical cultural diversity. Las
Verapaces is distributed across two Guatemalan provinces: Alta Verapaz and Baja
Verapaz (Figure 1.2 and 1.3). The geological structure of the area is primarily karstic
terrain of Cretaceous and Tertiary origin (Alta Verapaz), with metamorphic regions
dating from the Lower Paleozoic (Baja Verapaz and Alta Verapaz) (Ortega-Gutiérrez et
al., 2007).
1.6.1 Lachuá Lowlands
The Lachuá lowlands are located in a transitional zone between the Petén Lowlands and
the Cordilleran central highlands (Weyl, 1980) and contain one of the last remnants of
Lowland Rain Forest remaining in Guatemala (Figure 1.3) (for vegetation belt
description see results Chapter 2). The site has a protected area, the Lachuá Lake
National Park, which covers approximately 14,500 ha in addition to a surrounding buffer
zone of approximately 28,000 ha (Monzón, 1999). An inventory of Lachuá’s forest
species (as well as other vegetation types) was undertaken within the past 10 years
(García, 2001; Ávila, 2004; Cajas, 2009; Castañeda, 1997), and more recently, a modern
pollen reference collection of the thirty most abundant plant species has been collated
(Barrientos, 2006). There is a Lowland Rain Forest remnant (~300 ha) northeast of
16
Lachuá Lake National Park located in the top of a hill 285 masl in elevation with a series
of small ponds known as Tortugas (Tun personal communication, 2006). The remnant is
known as Salinas de los Nueve Cerros Regional Park, where an archaeological site of the
same name is located.
Geomorphologically, the area contains undulated karstic hills and varied landforms
ranging from low- to mid-elevations (170-600 masl) (Avendaño et al. 2007). The Lachuá
Lake is found at the Lachuá Lake National Park; a circular depression (400 hectares) with
a depth of 200 m, draining into the lower sedimentary basin of the Chixoy River
(Granados, 2001). Moisture-laden winds from the northwest and east originate from
within the Caribbean Sea, creating a mean annual precipitation of approximately 2000-
2499 mm. The rainy season occurs between May and October, with mean annual
temperatures between 25.5–28°C (Monzón, 1999).
1.6.2 Purulhá highlands
The Purulhá highlands cover the Cahabón River headwaters, and the Polochic and
Chixoy upper basins, ranging in elevation from 1560-2300 masl (Figure 1.3). Purulhá
contains a main remnant of cloud forest (1044 ha) that is protected under the jurisdiction
of “Biotopo Universitario para la Conservación del Quetzal” (BUCQ) (CONAP, 2000).
This site is underlain by the metamorphic and karstic system of the Sierra Chuacús
mountain range (Weyl, 1980). Moisture-laden Caribbean winds from the east, northeast,
and northwest result in mean annual precipitation around 2092 mm and mean annual
17
Figure 1.2. Location of Guatemala in Central America. Circle encloses location of the Las Verapaces Region. Numbers indicate locations of meteorological stations. 1= Flores, 2= Puerto Barrios, 3= Las Vegas, 4= Panzos, 5= Cahabón, 6=Papalhá, 7= Cobán, 8= Suiza Continental.
1
2346
57
8
MéxicoBelize
Honduras
NicaraguaEl Salvador
Costa Rica
Panama
Guatemala
Pacific Ocean
Caribbean Sea
Gulf of Mexico
1
2346
57
8
1
2346
57
8
MéxicoBelize
Honduras
NicaraguaEl Salvador
Costa Rica
Panama
Guatemala
Pacific Ocean
Caribbean Sea
Gulf of Mexico
18
Figure 1.3. Topographic map of the Las Verapaces Region in Guatemala. Encircled numbers indicate study sites. 1= Lachuá lowlands, 2=Sierra Chinajá, 3= Rio Tinajas, 4= Chelemhá, 5=Tucurú, 6= Tamahú, 7=Purulhá (BUCQ)-, 8= Tactic, 9= Santa Cruz Verapaz. Locations #6 to #9 are part of the Purulhá highlands. Watershed names are indicated in italics.
1
2
3
4
56
7
89
México
La Pasión
Chixoy
Cahabón
Polochic
1800 m
1000 m
200 m
Chinaja
Watershed boundary
1
2
3
4
56
7
89
México
1
2
3
4
56
7
89
1
2
3
4
56
7
89
México
La Pasión
Chixoy
Cahabón
Polochic
1800 m
1000 m
200 m
Chinaja
Watershed boundary
1800 m
1000 m
200 m
Chinaja
Watershed boundary
19
temperatures between 13.9–20.4°C (García, 1998). The rainy and dry seasons occur
between June and September and January and April, respectively. The Cahabón River
headwaters are located in the municipality of Purulhá town, province of Baja Verapaz, at
an elevation of approximately 1570 masl. The Cahabón River floodplain is characterized
by the presence of entisols and inceptisols in the low valley sections, surrounded by
andisols and ultisols in the surrounding mountains (MAGA, 2001). The floodplain is
located close to the upper limit of the Lower Montane Rain Forest (1000-1800 masl),
surrounded by valley slopes covered by Montane Cloud Forest (1800-2500 masl in my
study region) (for vegetation belts description see results Chapter 2). Local inhabitants
from Purulhá town have mentioned of the possible existence in the past of a lake in the
environs of the town (Vázquez C. personal communication 2011).
1.6.3. Geographical setting and study design
Vegetation sampling (Chapter 2) of lowland sites took place in separate watersheds: (1)
the Chixoy watershed which is composed of mainly Cretaceous-Tertiary marine
sediments and Quaternary alluvium, and (2) the Polochic watershed located over a pull-
apart type basin containing Quaternary alluvium (Fourcade et al., 1999). Highland sites
are located in the upland portions of the Cahabón and Polochic watersheds, which are
underlain by Pennsylvanian to Permian eclogitic rocks and gneisses (Ortega-Gutiérrez et
al., 2007). Rio Tinajas vegetation sampling sites are located in a sub-watershed that
drains into the Polochic Watershed (Tot, 2000).
20
Modern pollen samples for palynological calibration (Chapter 3) and core samples
(Chapter 4 and 5) were collected in two sites located at both ends of the Las Verapaces
elevational gradient (Figure 1.3): (1) Lowland Rain Forests at the Lachuá lowlands in
Alta Verapaz (~ 170 masl), and (2) the Montane Cloud Forest and the transitional
vegetation belt at the lower limit at the Purulhá highlands and its environs in Alta and
Baja Verapaz (~ 1400-2000 masl). The Purulhá highlands in our study region represent
the highest geographical point.
1.7 Cultural History of Study Region
According to the cultural succession and temporal differentiation for Mesoamerican
civilizations such as Olmec, Maya and Aztec (Chase et al., 2009), standardized periods
have been defined as the following: 1) Pre-Classic (3000 BC-300 AD), 2) Classic (300 -
900 AD), and 3) Post-Classic (900~1500 AD). These periods are delineated based on
critical changes to the political, economic and ceremonial development of Mesoamerican
civilizations. The most studied transition includes the end of the Classic Period of the
Maya Lowlands, known as the Terminal Classic Period (Demarest et al., 2004; Demarest,
2006).
Paleoecological studies in the Guatemalan Northern Petén Lowlands (Figure 1.2) have
reconstructed environmental changes dating back to the Last Glacial before any human
settlement took place in the region (Leyden, 2002), but emphasis has been placed on
Mayan cities that flourished mostly during the Classic Cultural period (300-900 AD)
(Islebe and Leyden, 2006). The heightened interest in this time period occurs mostly
21
because the majority of Classical cities underwent a regional transformation process at
the time of the Terminal Classic, largely known as Classic Mayan collapse (Aimers,
2007). Conclusions from some authors indicate that environmental anomalies, such as
droughts (Diamond, 2005; Gill et al., 2007), have played a critical role in determining the
fate of human societies, sometimes enhanced by human disturbances, which brought
together social instability and revolts due to natural resource demise. Contrasting research
approaches have concluded that environmental variability could have played more of a
secondary role on the transformation of societies, and that intrinsic societal characteristics
have a more relevant role in societal collapse (Demarest et al., 2004). This latter approach
emphasizes the idea that societies like the Mayan are able to cope with extrinsic
disturbances such as environmental extreme events, even when facing intrinsic
instabilities that requires substantial societal transformations.
Mesoamerican paleoecological research has provided explanations regarding the role of
environmental and societal factors on the shaping of landscapes along both highlands and
lowlands. Based on different fossil proxy evidence found in sedimentary records, some
lowland locations indicate the occurrence of drastic droughts, which are believed to have
had a dramatic impact on the transition between the Classic and Postclassic (900-1000
AD) . On the other hand, at some other locations experiencing possible arid events, there
were relatively few cultural changes or negative anthropogenic environmental impacts
even when human populations were highest. The Classic-Postclassic transition is
delineated mostly as a socio-political and religious transformation, that in some locations
promoted total or temporary abandonment of cities, semi-destruction due to warfare,
22
while in other locations, cultural flourishment took place (Demarest, 2009). Evidence
indicates that the most dramatic changes to all aspects of the Mayan Culture and the
environment occurred during the Spanish Conquest and Colonization (Elliot et al. 2010).
The Spanish settlers brought new diseases that contributed in part to the Mayan
population demise, and ultimately the introduction of new economic, political,
sociological, and religious systems (Van Buren 2010).
There is an obvious void in the Mesoamerican paleoecological record that must be filled
due to the contextual importance of the Las Verapaces region. The Las Verapaces
lowlands represent an important geographical transition from the Northern Petén region
to the Las Verapaces Highlands, and Southern Maya Area (i.e. Kaminal Juyu, Copán, and
Takalik Abaj) (Rice et al., 1985; Fowler et al., 1989). The lack of paleoecological
information for the Las Verapaces Region places this thesis as critical for providing
information about the landscape evolution of the last two millennia. Natural and cultural
factors have been explored in this thesis to provide a baseline for continuing
paleoecological research in this region as well as in neighboring regions in Mesoamerica.
The Lachuá lowlands are located east of the neighboring Petexbatún cultural region
where important cities were developed along the Pasión and Chixoy rivers banks
(Demarest, 2006). The Petexbatún region had different political elites that established a
succession of Kingdoms, where military control was critical to maintain privileged
economic riverine routes. Cancuen, located approximately 60 km east of Lachuá, was an
important city since the late Pre-Classic until its abandonment during the Late Classic
23
(Aimers, 2007). Paleoecological and paleoagronomic evidence from the Petexbatún
lowlands indicate that sustainable agriculture and forestry were practiced in succession
(Demarest, 1997). Sustainable management practices likely involved soil conservation to
mitigate environmental deterioration with time (Beach and Dunning, 1995; Beach et al.,
2008; Dunning et al., 1997).
At the Lachuá lowlands, the ancient city of Salinas de los Nueve Cerros was established
as an important salt producing center along the Chixoy river banks (Figure 1.4) (Dillon,
1977; 1990; Garrido, 2009). There is no direct evidence describing landscape
management practices, but it is possible that similar soil ammendment measures observed
in the Petexbatún region were also occuring in Salinas de los Nueve Cerros.
Archaeological studies indicate that the economic importance of the Mayan site of
Salinas de los Nueve Cerros was salt production practiced from the Preclassic to Post-
Classic times. At present, population pressure in the Lachuá Region is beginning to
encroach on the Lachuá Lake National Park and Salinas de los Nueve Cerros; over the
past 50 years, 50% of the forest has been lost to anthropogenic land-use change
(Avendaño et al, 2007). The population generally consists of people from the q’eqchi’
ethnic group who mostly ended up in the region as a result of territorial displacement and
colonization projects following the Civil War (Hurtado, 2008).
In order to better understand the cultural processes that were taking place in the Maya
Lowlands, it is critical to concomitantly address the environmental and cultural history of
the Maya Highlands. The scarcity of lakes on the one hand explains why highlands (i.e.
24
Figure 1.4. Topographic map of study sites in the Las Verapaces Region in Guatemala. Map I= Lachuá lowlands, Map II= Purulhá highlands. Bryophyte polsters are indicated in letters and surface sediments in numbers. 1= L1, 2= L2, 3= L3, 4= Sa2 (Salinas de los Nueve Cerros archaeological site and natural reserve), 5=J1, 6= T1, 7= P4, 8= P1, A=samples Ca-Ce, B= samples Ra-Re. Both A and B are located at the Lachuá Lake National Park. C= Samples N1-N10 (“Biotopo Universitario para la Conservación del Quetzal”). Highland archaeological sites: VP=Valpraiso, CH= Chican, CX= Cerro Xucaneb, S= Sulin. National parks are represented as dark grey polygons. Rivers are irregular black thick lines. Lachuá Lake is represented as light gray polygon in map I. Chichoj Lake is represented as light gray polygon in map II. Samples 6-8 are located in the Cahabón River Floodplains. Isolines every 50 m in Map I (lowest point 150 masl, highest point 700 masl). Isolines every 100 m in Map II (lowest point 1400 masl, highest point 2300 masl).
25
Las Verapaces) paleoecological research lags behind its lowlands counterpart. But on the
other hand, this scarcity is related to the main interest of researchers in wanting analyze
paleoenvironmental records related to archaeological findings from major Classic Maya
centers which were distributed mostly in Mesoamerican lowlands (Anselmetti et al.,
2006; Hillesheim et al., 2005; Wahl et al., 2007). This trend has dominated despite of the
importance that the multi-factorial interaction (i.e. political, economical, ceremonial, etc.)
lowlands-highlands had for the development of the Maya Civilization during the last
3000 years (Freidel et al., 1993). Nevertheless, recently there has been an increase in
addressing paleoecological questions related to highlands environments in Mesoamerica
(Almeida et al., 2005).
There is scarce paleoecological information about highlands landscape management
practices, but archaeological investigations indicate that relatively high gradient
environmental (e.g. topographic) boundaries promoted the evolution of relatively small
(regional) and well-bounded cultural systems (Sharer and Sedat, 1987). In the Purulhá
highlands, there are many minor archaeological sites that range from the Pre-Classic to
the Post-Classic, including such sites as Cerro Xucaneb, Chican, Sulin, and Valparaiso
(Figure 1.4) (Arnauld, 1978, 1987; Ichon et al., 1996). In contrast to the lowlands,
expansion and alliances of these highland cultural entities was limited in part to
constrained communication over mountainous landscapes, and not strictly to economic,
social, political and ideological factors (Ichon et al., 1996). Natural trade routes have
been traced between lowland and highland archaeological sites that cross mountain ridges
and valleys, therefore indicating that commerce and cultural interregional exchange were
26
occurring at this time (Andrews, 1984). It is precisely the connection between disparate
regions that was important for the development of the Maya Civilization (Arnauld, 1997).
It is the exchange of socio-political, cosmological and ceremonial knowledge, in addition
to landscape management practices, that unifies the Mayan cultural region. Little has
been discussed about the Mayan Highlands terminal Classic and the occurrence of city-
center collapse (Demarest, 2009). There is need for further investigation about what
causes some cities to be abandoned while others to be founded and flourished.
Land-use at the Purulhá highlands during the late-19th century was dominated by coffee
plantations, whereas today the area is dominated by a complex mosaic of cattle fields,
agricultural crops (mainly corn), and ornamental species. Population density in this
highland area (primarily comprising achi, poqomchi’, q’eqchi’, and ladino ethnic groups)
is steadily increasing, and has created an ever heightening demand for land for agriculture
and urbanization (CONAP, 2000). Following European conquest (ca. 500 yrs BP) socio-
economic and political pressures led to dramatic changes in (1) land-use patterns (i.e.
introduction of cash crops and plantations), (2) foreign investment, and (3) displacement
of indigenous populations (Van Buren, 2010). More recently, anthropogenic disturbances
associated with civil war, strong military rule, colonization, deforestation and pollution
related to natural resource extraction (i.e. mining) have contributed to the character of the
landscape in the Las Verapaces Region (Hurtado, 2008).
27
Chapter 2:
Vegetation Distribution along the Las Verapaces region in North Central Guatemala
2.1 Introduction
Understanding the controls on vegetation distribution in the tropics will improve
predictions of responses to future climate change (Freycon et al., 2010) and help to better
determine factors behind centers of high biological diversity ("biodiversity"). Climate is
usually considered a first-order control on vegetation type and distribution (Tietjen et al.,
2010); however, other factors such as watershed topography (Bertoldi et al., 2010) and
evolutionary history (Vanderpoorten et al., 2010) can also play critical roles in shaping
biogeography. Guatemala currently does not have a formal protocol for describing
vegetation types or belts based on floristic and environmental criteria, however, the
following approaches have been used in the past: (1) qualitative integrations of flora with
physiographic and geomorphologic factors (Villar, 1998), (2) quantitative local
adaptations of Holdridge Life Zones (De La Cruz, 1982), or (3) qualitative adaptations of
classifications from neighboring regions like Mexico (Rzedowski, 2006). More
formalized vegetation identification surveys are needed, particularly in light of the fact
that Guatemala is located in Nuclear Central America and is home to the Mesoamerican
Tropical Forest Hotspot (Harvey et al., 2008). The Mesoamerican hotspot is renowned for
its high vegetation diversity (Knapp and Davidse, 2006), despite being located in an area
influenced by humans for over the past 7,000 years (Chinchilla, 1984). Guatemala’s rich
28
biological and cultural complexity highlight the necessity for better understanding the
roles of natural and cultural factors in vegetation distribution.
The first research objective is to identify changes in vegetation communities and to
delineate boundaries between vegetation belts along an elevational gradient located in the
Purulhá highlands and the Lachuá lowlands of the Las Verapaces region in north central
Guatemala. The names of the vegetation belts applied for Las Verapaces region were
adapted and integrated from different vegetation regional studies (Breedlove, 1981; de la
Cruz, 1982; Kappelle et al., 1995; Kappelle, 1996; Domínguez-Vázquez et al., 2004)
(Table 2.1): (a) Lowland Rain Forest below 1000 masl, (b) Lower Montane Rain Forest
between 1000 and 1800 masl and (c) Montane Cloud Forest above 1800 masl up to
approximately 2500-3000 masl. Other vegetation belts found in neighbouring regions
include (de la Cruz, 1982; Islebe and Kappelle, 1994; Islebe and Velázquez, 1994; Islebe
et al., 1995) (Table 2.1): (d) Lowland Humid Forest, with less precipitation than the
Lowland Rain Forest, such as in the northern Petén region; (e) Montane Mixed Forest,
where the endemic tree Abies guatemalensis is found; (f) Sub-Alpine Forest, being the
tree line limit in Guatemalan forests; and (g) Páramo (Alpine bunchgrassland), in the
Sierra de los Cuchumatanes and in the Western Volcanic Chain.
In order to achieve the first research objective a meta-data analysis of different local
literature sources has been created, where the distribution of plant taxa within one site or
among different sites in the elevation gradient is included. The existence of plant taxa
with discrete elevational distributions is responsible for the delineation of vegetation
29
Table 2.1 Description of vegetation belts found in the Las Verapaces region* and neighbouring regions in Guatemala. Vegetation Belt
Elevation range (masl)
Mean annual precipitation (mm)
Associated plant taxa
Lowland Humid Forest
~ 0 to <600
~1100-1700
Alseis yucatanensis, Aspidoderma megalocarpon, Manilkara zapota, Sabal morisiana.
Lowland Rain Forest*
~ 0 to 1000
~2100-4300
Sapium, Terminalia amazonia, Trema, Ulmus.
Lower Montane Rain Forest*
~ 1000 to 1800
~2000-2500
Alchornea, Croton draco, Persea schiediana, Rapanea, Myrica.
Montane Cloud Forest*
~1800 to 2500-3000
~ >4100
Hedyosmum mexicanum, Quercus, Podocarpus oleifolius.
Mixed Montane Forest
~ 2500 to 3000-3100
~2500
Abies guatemalensis, Alnus, Pinus ayacahuite, P. montezumae, Quercus.
Sub-Alpine Forest
~ 3100 to 3800
~1100-1800
Alnus, Buddleja, Juniperus, Pinus hartwegii.
Páramo (Alpine bunchgrassland)
~ >3800
~1275
Cardamine, Poa venosa, Senecio, (Sierra de los Cuchumatanes); Calamagrostris, Luzula, Halencia, Oxylobus, Poa tacanae (Western Volcanic Chain).
30
belts; alternatively, plant taxa that have more continuous distribution create landscape
continuums (Kessler, 2000; Hemp, 2006).
The second objective is to evaluate the factors responsible for vegetation distribution and
turnover of plant communities along the Las Verapaces region. Three key deriving
factors will be examined: (1) elevation and associated changes in climate (i.e.
environmental lapse rate), (2) landscape position and topography in drainage divides, and
(3) biogeographic origin (i.e. over geological timescales). The findings from this analysis
will also provide a critical baseline from which to conduct palaeoecological research
because we can relate fossil pollen spectra to indicator taxa from modern-day vegetation
belts. Ultimately, by studying the natural (biotic, abiotic) factors influencing vegetation I
can begin to tease apart complex interactions between the natural environment and
anthropogenic processes.
2.2 Methods
2.2.1 Compilation of the vegetation database
For areas with few published records, forest inventory databases and unpublished
academic theses provide a rich source from which to better understand the biotic and
abiotic factors influencing vegetation trends observed across modern-day landscapes
(Kitahara et al., 2009; Veen et al., 2010). Data on vegetation community composition,
plant species identification and abundance were collected from multiple sources
including silvicultural, ecological and landscape research reports (Table 2.2). Five out of
31
ten of the sources report ecological data using traditional experimental design, including
large sample sizes and multiple replicates. Dissertation research conducted by University
students in Guatemala was invaluable to the collation of the database. These sources
included: (1) four undergraduate theses from Lachuá (Ávila, 2004; Cajas, 2009),
Purulhá (García, 1998), and Chelemhá (López, 2009.), (2) one Master of Science thesis
from Sierra Chinajá (Bonham, 2006), and (3) forestry inventories extracted from
undergraduate theses for Tucurú (Paz, 2001), Tamahú (Alonso, 1999), Santa Cruz
(Palala, 2000), Tactic (Mollinedo, 2002), and Rio Tinajas (Tot, 2000).
Because six studies only presented qualitative data (presence/absence), sources that had
quantitative data (abundances) were transformed to presence/absence to standardize my
database. Taxonomic nomenclature was also standardized when necessary and updated
(Gentry, 1982; Smith et al., 2004). In some cases, standardization required retention of
genus-level information only, correction of spelling, and revision of taxonomic
synonymies. The end result is a matrix showing distributions (presence/absence) of 794
angiosperm taxa across 23 sampling units.
Although I recognize the ecological, biogeographic and economic importance of
gymnosperms, I am not incorporating them in my study because in Guatemala little
information on their distributions is available outside of a plantation/forestry context.
Therefore, my analysis focuses on exclusively angiosperms.
32
2.2.2 Creation of climate databases
To create a regional climate database for sites along our selected gradient, I used
information from eight meteorological stations located in Central and Northern
Guatemala (Figure 1.1). Data from seven stations at different elevations were collected
directly from INSIVUMEH (Volcanology, Meteorology, and Hydrology National
Institute) in Guatemala City, each having temporal coverage from the years 1990-2005
inclusive. From a longer climate database (42 years; 1961-2003) (Aguilar et al., 2005),
data from Flores (123 masl) was used for my analysis. Of all meteorological variables
available, I selected three temperature variables that best represent both extremes and
average indicators of regional climate. The chosen variables include: (1) maximum
absolute temperature (TXx) defined as the recorded annual maximum value of daily
maximum temperature, (2) minimum absolute temperature (TNn) defined as the recorded
annual minimum value of daily minimum temperature, and (3) mean annual temperature
(MAT). Temperature parameters such as MAT have been used to estimate upper limits of
low-elevation taxa (Latorre et al., 2006), and TNn and TXx are useful to estimate
physiological barriers for plants survival (e.g. drop of temperatures close to overnight
frosting and dessication stress related high temperatures, respectively).
2.2.3 Statistical Analysis
A multivariate analysis was run on a total of 794 angiosperm plant taxa from nine sites
with a total of 23 sampling units (presence/absence data), to determine the degree of
similarity between sites and the relationships between taxonomic assemblages and
climate variables. Through a detrended correspondence analysis (DCA) sites were
33
arranged in a diagram along ordination axes to indirectly identify possible underlying
environmental gradients (Jongman et al., 1995). The presented DCA diagram presents
axis scores transformed into percentages to help visualize the data variability (McCune
and Mefford, 2006). I created dendrograms through hierarchical cluster analysis (HCA)
(relative Euclidean distance and Unweighted Pair Group Method Algorithm; UPGMA) of
sites with similar taxonomic composition, which were of aid to establish groups of sites
in the DCA diagram (Jongman et al., 1995). Where consistent agglomeration of sites was
observed through ordination axes and cluster analysis, a vegetation belt was delineated as
a correlation of elevation and species composition (Axis scores). The software PC-Ord
was used to conduct all statistical analyses (McCune and Mefford, 2006). Plant taxon that
presented a unique DCA Axis 1 score were chosen as representative of a particular
distribution pattern along the altitudinal gradient, instead of utilizing a group of taxa with
the same Axis 1 score. Species scores are known to represent a particular site or groups
of sites, as DCA Mode-Q analysis indicates that sites are “centroids” for an assemblage
or array of determined species (Jongman et al., 1995). Species and sites scores are known
to be illustrative of each other (Chase et al. 2000).
As mentioned earlier, the names of the vegetation belts and their elevation limits were
established a priori (Table 2.1): (a) Lowland Rain Forest below 1000 masl, (b) Lower
Montane Rain Forest between 1000 and 1800 masl and (c) Montane Cloud Forest
between above 1800 and 2500 masl. Indicator taxa were defined as those found
exclusively inside a vegetation belt (i.e. in a discrete elevation range like 1000-1800
masl) whereas generalist taxa are those with a wide distribution that span across one or
34
Table 2.2. Sites included in the vegetation database of the Las Verapaces region, providing a total of 23 sampling units (SU) from 10 studies spanning an elevation gradient of 170 to 2532 masl. Where indicated, elevation ranges used to calculate average elevations are shown in parentheses. If researchers pooled sampling units (SU) of a site into one vegetation data set, the average elevation was calculated for the site. When sampling units of one site were not pooled, their elevations and corresponding vegetation data were entered directly into our database. If elevation ranges for sampling units were given, the average elevation was calculated. For data type, Q indicates studies that used abundance as measurement and C indicates studies that used presence/absence as measurement. Source Ávila (2004)
and Cajas (2009)
Bonham (2006)
Paz (2001) Alonso (1999)
Palala (2000)
Mollinedo (2002)
Tot (2000) García (1998)
López (2009)
Sites Lachuá (n=1)
Sierra Chinajá (n=1)
Tucurú (n=3)
Tamahú (n=1)
Santa Cruz (n=1)
Tactic (n=1)
Rio Tinajas (n=6)
Purulhá (n=5)
Chelemhá (n=4)
SU codes (in bold)
Lach Chin
Buena Vista (Bvta) Cumbre de Florida, (Flo) Chelemá (Che)
Tam Scruz
Tac
Tin1 Tin2 Tin3 Tin4 Tin5 Tin6
Pur1 Pur2 Pur3 Pur4 Pur5
Che1 Che2 Che3 Che4
Elevation (m asl)
170 400 (200-600)
1200 1100 1260
1048 1500 1650 200 (0-400) 600 (400-800) 1000 (800-1200) 1400 (1200-1600) 1800 (1600-2000) 2200 (2000-2400)
1800 1900 2000 2100 2200
1900 (1800-2000) 2100 (2000-2200) 2300 (2200-2400) 2466 (2400-2532)
Data Q C C C C C C Q Q Watershed (see Fig. 1.3)
Chixoy Chixoy Polochic Polochic Cahabón Cahabón Tinajas/ Polochic
Cahabón /
Polochic
Cahabón / Polochic
35
two neighboring vegetation belts (i.e. from 400 to 1800 masl). I defined disjunctive taxa
as those found at two discrete vegetation belts but not in three (i.e. 400 and 1800 masl).
Disjunctive taxa were considered when they were distributed in two non-neighboring
elevation belts. I created my plant checklist based on taxa from these three different
categories (indicator, generalist, and disjunctive). DCA Axis 1 scores were used as
representative of vegetation composition at each of the sites and Axis 1 scores were
regressed against elevation.
Indicator, generalist and disjunctive plant taxa were allocated to one of Gentry’s (1982)
four paleogeographic categories: (1) Laurasian, (2) Amazonian-centered, (3) Andean-
centered, and (4) Miscellaneous. A chi-square contingency table test was run to analyze
the relationship between these categories and their corresponding vegetation belts.
Equations were constructed to describe the relationship between elevation and
temperature (temporal average for each meteorological station) to determine the lapse
rate. To predict the value of the chosen parameters for our study sites according to their
elevation, an interpolation was performed for sites located between 2 masl (Puerto
Barrios) and 2100 masl (Suiza Continental) in elevation, and an extrapolation was
performed for sites with elevations higher than Suiza Continental.
2.3 Results
2.3.1 Ordination and grouping of sites and plant taxa
A linear regression of the DCA Axis 1 scores of sites and their elevation showed a
significant correlation (r2=0.53, p<0.01), and sites were ordered from lowlands to
36
highlands (Figure 2.1 and 2.2). Based on the DCA diagram I identified the three
expected vegetation belts according to their elevation and related Axis 1 site scores
(Figure 2.2): (a) Lowland Rain Forest below 1000 masl, (b) Lower Montane Rain Forest
between 1000 and 1800 masl and (c) Montane Cloud Forest above 1800 masl. Axis 1
scores of indicator taxa combined against their average elevation, showed a significant
correlation to elevation (r2=0.80, p<0.0001; Figure 2.2 A).
2.3.2 Climate-elevation-species relationships
Although there was considerable variation in climatic variables between and within
meteorological stations, I found a strong linear relationships between temperature and
elevation (r2= 0.65–0.87) (Figure 2.3). Based on these estimations, the environmental
lapse rate of temperature is approximately 0.5°C/100 masl, close to the expected
theoretical value of 0.6°C /100 masl. Variations in correlations may be due to one, or a
combination, of two factors: (1) highly localized weather variability, and (2) insufficient
size of climatic data and/or missing data points. Based on my equations of climate
parameter by elevation, I could identify temperature ranges associated with each of the
three identified vegetation belts.
According to my climate data model for the elevation ranges associated with Lowland
Rain Forest, mean annual temperature (MAT) ranges from 19.9-25.3°C, maximum
absolute temperature (TXx) ranges from 32.2-36.1°C, and minimum absolute temperature
(TNn) ranges from 6.8- 12.3°C. For Lower Montane Rain Forest, MAT ranges from 16.7-
19.9°C, TXx ranges from 32.0-33.2°C, and TNn ranges from 5.2-6.8°C. For Montane
37
0
0
40 80
20
40
60
80
Axis 1
Axis 2
MCF
MCF
LRF
LMRF -W
MCF LMRF - E
LMRF - E
LRF
MCF
Chelemhá
LRF
Tinajas- E
Lach
Chin
Tin1
Tin2
Tin3
Scruz
Tam
Tac
Che Pur1
Pur2
Pur3Pur4
Pur5
Tin4
Tin5
Tin6
Flo
Bvta
Che3
Che2Che1
Che4
0
0
MCF Purulhá
LRF
- E
LRF
LRF Tinajas
Tin1
Tin2
Tin3 Che Pur1
Pur2
Pur3Pur4
Pur5
Tin4
Tin5
Tin6
Flo
Bvta
Che4
0
0
40 80
20
40
60
80
Axis 1
Axis 2
MCF
MCF
LRF
LMRF -W
MCF LMRF - E
LMRF - E
LRF
MCF
Chelemhá
LRF
Tinajas- E
Lach
Chin
Tin1
Tin2
Tin3
Scruz
Tam
Tac
Che Pur1
Pur2
Pur3Pur4
Pur5
Tin4
Tin5
Tin6
Flo
Bvta
Che3
Che2Che1
Che4
0
0
MCF Purulhá
LRF
- E
LRF
LRF Tinajas
Tin1
Tin2
Tin3 Che Pur1
Pur2
Pur3Pur4
Pur5
Tin4
Tin5
Tin6
Flo
Bvta
Che4
Figure 2.1. Detrended Correspondence Analysis diagram of Las Verapaces sites along the first two DCA axes. Sites enclosed by ovals represent groups identified in the Hierarchical Cluster Analysis (HCA). LRF= Lowland Rain Forest sites, LMRF= Lower Montane Rain Forest sites, MCF= Montane Cloud Forest. W= West, E= East.
38
y=3.85x+243
r2=0.80
y=3.04x+497.2
r2=0.53
y=3.85x+243
r2=0.80
y=3.04x+497.2
r2=0.53
Figure 2.2. Linear regression of Detrended Correspondence Analysis (DCA) Axis 1 scores (raw scores) of indicator plant taxa (A) and sites (B) against elevation values per site along the Las Verapaces gradient. LRF= Lowland Rain Forest, LMRF= Lower Montane Rain Forest, MCF= Montane Cloud Forest. The dashed square in panel B refers to Tin5 MCF sampling unit.
39
Figure 2.3. Linear regression curves of temperature (°C) variables collected from meteorological stations from Central and Northern Guatemala. A) TXx = maximum absolute temperature, B) TNn = minimum absolute temperature, and C) MAT= mean annual temperature. Diamonds represents the mean temporal value for the period reported in the station, and dots represent the temporal variation over the length of the record. MAT is taken from 6 stations, and TXx and TNn from 7 stations (see Figure 1.2. for stations locations).
Elevation (m)
0 500 1000 1500 2000 2500
TXx
22
24
26
28
30
32
34
36
38
40
42
Elevation (m)
0 500 1000 1500 2000 2500
MA
T
16
18
20
22
24
26
28
30
Elevation (m)
0 500 1000 1500 2000 2500
TNn
0
5
10
15
20
25
30
r2 =0.79
r2 =0.87
r2 =0.65
Elevation (m)
0 500 1000 1500 2000 2500
TXx
22
24
26
28
30
32
34
36
38
40
42
Elevation (m)
0 500 1000 1500 2000 2500
MA
T
16
18
20
22
24
26
28
30
Elevation (m)
0 500 1000 1500 2000 2500
TNn
0
5
10
15
20
25
30
Elevation (m)
0 500 1000 1500 2000 2500
TXx
22
24
26
28
30
32
34
36
38
40
42
Elevation (m)
0 500 1000 1500 2000 2500
MA
T
16
18
20
22
24
26
28
30
Elevation (m)
0 500 1000 1500 2000 2500
TNn
0
5
10
15
20
25
30
r2 =0.79
r2 =0.87
r2 =0.65
°C°C
°C
Elevation (m)
0 500 1000 1500 2000 2500
TXx
22
24
26
28
30
32
34
36
38
40
42
Elevation (m)
0 500 1000 1500 2000 2500
MA
T
16
18
20
22
24
26
28
30
Elevation (m)
0 500 1000 1500 2000 2500
TNn
0
5
10
15
20
25
30
r2 =0.79
r2 =0.87
r2 =0.65
Elevation (m)
0 500 1000 1500 2000 2500
TXx
22
24
26
28
30
32
34
36
38
40
42
Elevation (m)
0 500 1000 1500 2000 2500
MA
T
16
18
20
22
24
26
28
30
Elevation (m)
0 500 1000 1500 2000 2500
TNn
0
5
10
15
20
25
30
Elevation (m)
0 500 1000 1500 2000 2500
TXx
22
24
26
28
30
32
34
36
38
40
42
Elevation (m)
0 500 1000 1500 2000 2500
MA
T
16
18
20
22
24
26
28
30
Elevation (m)
0 500 1000 1500 2000 2500
TNn
0
5
10
15
20
25
30
r2 =0.79
r2 =0.87
r2 =0.65
°C°C
°C°C
°C
40
Cloud Forest, MAT ranges from 13.9-16.1°C, TXx ranges from 26.7-30.4°C, and TNn
ranges from 4.0-4.9°C.
2.3.3 Role of landscape position and watershed topography
Although elevation appears to be an important factor controlling plant taxa differences
between sites, the multivariate analyses show that other factors are important as well. The
arrangement of sites along the DCA axes responds possibly to landscape position which
was further confirmed through the HCA dendrogram (Figure 2.1). Lachuá and Chinajá
are both Lowland Rain Forest sites yet they show a separation on the ordination diagram
likely due to topographical factors (i.e. Lachuá flatlands versus Sierra Chinajá).
According to HCA, sampling units from Tinajas watershed were separated according to
elevation in the three vegetation belts. Lower Montane Rain Forest sites were separated
in two main groups according to their geographical location: east and west. The east
group consisted of the Tucurú sampling units and the west group included Tactic, Santa
Cruz and Tamahú sites. The Montane Cloud Forest sites were allocated into sub-groups
as a function of their location in three different ridges separated by valleys (Figure 1.2):
Sierra de Las Minas, Sierra Chuacús, and Sierra Yalijux.
2.3.4 Species assemblages and indicator species
Using regression of DCA Axis scores against elevation for each taxon, I sorted the
original 794 angiosperm plant taxa into 26 indicator, 20 generalist, and 9 disjunctive plant
taxa whose distributions were zonal, continuous and discontinuous (respectively) along
the elevational gradient. These categories allowed me to more clearly correlate vegetation
41
with elevation, geographical conditions, and in turn, with climate. The remaining taxa
(739) did not present a unique DCA Axis 1 score, as many plant taxa shared the same
score. The identified indicator taxa were related to the elevational range of one of three
vegetation belts (Table 2.3). In terms of generalist taxa (Table 2.4) there were 14 taxa
common across Lowland Rain Forest and Lower Montane Rain Forest, 11 taxa common
across Lower Montane Rain Forest and Montane Cloud Forest, and 2 taxa across all three
vegetation belts. Disjunctive taxa (Table 2.5) were distributed in both Lowland Rain
Forest and Montane Cloud Forest.
2.3.5 Biogeographical affinities
There is an increase in Laurasian and Andean indicator taxa, and a decrease in
Amazonian taxa, when moving from Lowland Rain Forest to Montane Cloud Forest
(Figure 2.4). The generalist taxa common to Lowland Rain Forests and Lower Montane
Rain Forests are all Amazonian-centered taxa. Andean-centered and Laurasian generalist
taxa are only common between Lower Montane Rain Forest and Montane Cloud Forest
(Figure 2.4). Andean-centered taxa co-dominate the disjunctive taxa with Amazonian-
centered taxa, and to a much lesser extent, the unassigned taxa to a particular origin.
According to the chi-square contingency test, the frequencies observed of biogeographic
categories along vegetation zones are not at all likely explained by chance (Χ2= 35.00, df
=8, p<0.0001).
42
2.3.6 Study Limitations: sampling effects
The sites included in this study can be separated into two groups according to their
sampling effort: high intensity sampling, representing a detailed collection of plants
(understory, subcanopy and canopy layers) along the spatial variability of an
environmental gradient (Purulhá, Chelemhá, Lachuá and Chinajá) and low intensity
sampling (Tucurú, Tamahú, Santa Cruz, Tactic, and Rio Tinajas). Many studies indicate
that sampling effort is directly related to species richness and diversity (Shen et al.,
2003). Low intensity sampling studies (e.g. mainly focused on forest inventories) are
likely to result in the collection of mostly abundant and generalist species than rare and
specialist species (Pitman et al., 2001). Most of the generalist plant taxa were found in the
Lower Montane Forest which includes exclusively the low intensity sampling sites
(Figure 2.2b).
The pattern found in the Las Verapaces region could be affected by differences in the
research objective of each study, experimental designs, and sampling efforts (Otypková
and Chytry, 2006). This limitation is significant to recognize because most of the
information on vegetation is in low intensity format for Guatemala (i.e. as it is over the
rest of the tropics) (Mathewson, 2006). Nevertheless, after being made aware of the
possible caveats and weaknesses, I found that the combination of information from both
low and high sampling effort studies allowed me to differentiate three vegetation belts
and explain their delineation based on elevation and climate, landscape position and
watershed topography, and biogeographic origin (Figure 2.1 and 2.2).
43
Vegetation belt Family Biogeographic originLowland Rain ForestGenipa sp. RUBIACEAE ANSpondias mombim ANACARDIACEAE AMZTabebuia sp. BIGNONIACEAE AMZ
Lower Montane Rain ForestCedrela pacayana MELIACEAE AMZHeliocarpus mexicanus TILIACEAE AMZInga sp. FABACEAE AMZPerymenium grande ASTERACEAE ANSaurauia belisensis ACTINIDIACEAE LAU
Montane Cloud ForestBegonia oaxacana BEGONIACEAE ANCavendishia guatemalensis ERICACEAE ANCentropogon cordifolius CAMPANULACEAE ANClethra suaveolens CLETHRACEAE LAUErigeron karvinskianus ASTERACEAE ANFuchsia microphylla ONAGRACEAE ANLobelia nubicola CAMPANULACEAE ANMiconia aeruginosa MELASTOMATACEAE ANMiconia glaberrima MELASTOMATACEAE ANOcotea sp. LAURACEAE AMZOreopanax liebmanii ARALIACEAE ANPassiflora sexflora EUPHORBIACEAE AMZPhoradendron sp. LORANTHACEAE ANPsychotria parasitica RUBIACEAE ANRhynchosia sp. FABACEAE AMZStyrax argenteus STYRACACEAE LAUSynardisia venosa MYRSINACEAE ANWeinmannia pinnata CUNIONIACEAE AN
Table 2.3 Indicator plant taxa for the three vegetation belts along the Las Verapaces region, selected from DCA axis scores for species (see text for details). AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.
44
Vegetation belts Family Biogeographic originLRF-LMRFBursera simaruba BURSERACEAE AMZCecropia peltata CECROPIACEAE AMZCeiba pentandra BOMBACACEAE AMZParathesis vulgata MYRSINACEAE ANTerminalia amazonia COMBRETACEAE AMZVirola sp. MYRYSTICACEAE AMZVochysia guatemalensis VOCHYSIACEAE AMZ
LMRF-MCFBillia hippocastanum HIPPOCASTANACEAE LAUBrunellia mexicana BRUNELLIACEAE ANDendropanax leptopodus ARALIACEAE ANEngelhardtia guatemalensis JUGLANDACEAE LAUEupatorium semialatum ASTERACEAE ANHedyosmum mexicanum CHLORANTHACEAE LAULiquidambar styraciflua HAMMAMELIDACEAE LAUMyrica cerifera MYRICACEAE LAUPersea donnell-smithii LAURACEAE AMZQuercus crispifolia FAGACEAE LAUQuercus sp. FAGACEAE LAU
LRF-LMRF-MCFClusia sp. CLUSIACEAE ANMollinedia guatemalensis MONIMIACEAE AN
Table 2.4 Generalist plant taxa for the Las Verapaces region, as determined by DCA axis scores for species (see text for details). AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.
45
Table 2.5. Disjunctive plant taxa distributed in Lowland Rain Forest and Montane Cloud Forest in the Las Verapaces region generated from DCA axis scores for species (see text for details). AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.
Disjunctive taxa Family Biogeographic origin
Clidemia capitellata MELASTOMATACEAE AN Conyza bonariensis ASTERACEAE AN Dendropanax arboreus ARALIACEAE AN Lasciacis divaricata POACEAE Unassigned Matayba oppositifolia SAPINDACEAE AMZ Ocotea eucuneata LAURACEAE AMZ Peperomia cobana PIPERACEAE AN Phoebe sp. LAURACEAE AMZ Pouteria campechiana SAPOTACEAE AMZ
46
Figure 2.4. A) Indicator (in one vegetation belt) and B) generalist (across two vegetation belts) taxa separated according to their biogeographic origin along the Las Verapaces region vegetation belts (increasing in elevation from left to right) (for indicator taxa Χ2= 35.00, df =8, p<0.0001). LRF=Lowland Rain Forest, LMRF=Lower Montane Rain Forest, MCF=Montane Cloud Forest, AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.
0%
20%
40%
60%
80%
100%
LRF LMRF MCF
LAUANAMZ
A
0%
20%
40%
60%
80%
100%
LRF LMRF MCF
LAUANAMZ
A
0%
20%
40%
60%
80%
100%
LRF-LMRF LMRF-MCF LRF-LMRF-MCF
LAUANAMZ
B
0%
20%
40%
60%
80%
100%
LRF-LMRF LMRF-MCF LRF-LMRF-MCF
LAUANAMZ
B
47
2.4 Discussion
2.4.1 Elevation and climate
Climatic dynamics along elevation is possibly the first-order explanatory factor in
understanding modern-day vegetation trends in our study region in Guatemala, as is
found with other Latin American countries (Quintana-Ascencio and González-Espinosa,
1993; Gerold et al., 2008) and generally world-wide (Hemp, 2006; Kappelle et al., 1995).
The arrangement of sites along Axis 1 in the DCA diagram shows a clear relationship
between floristic composition and elevation (Figure 2.2). Elevation-species interactions
are the result of the environmental lapse rate; in other words, changes in climate
associated with distance from sea level (Figure 2.3). Temperature data for each
vegetation belt generally corresponds to Holdridge’s Life Zones in Guatemala (De La
Cruz, 1982) that are themselves defined mostly as a function of climate. After reviewing
information for vegetation belts across Central America and Mexico (Islebe and
Kappelle, 1994; Islebe and Velázquez, 1994), elevation and its correlation with
temperature variability is found to be a common factor for differentiation of vegetation
belts.
Within a given elevation, my data highlight some unexpected differences in vegetation
composition, indicating that maybe broad-scale climatic changes dictated by the
environmental lapse rate are only part of the explanation for plant species turn-over
through space and time. Studies of tropical forests in Hawai'i (Crausbay and Hotchkiss,
2010), Venezuelan Andes (Cuello and Cleef, 2009) and the Chihuahuan Borderlands
(Poulos and Camp, 2010) indicate that factors such as strong moisture gradients,
48
topography, and incident solar radiation are important to define changes in vegetation.
Lachuá’s dissimilarity to Chinajá (Figure 2.1) within the Lowland Rain Forest belt, for
example, may be due to variations in local microclimate. On the one hand, Chinajá
vegetation is located in an isolated topographic feature (e.g. approximately 500 m higher
than Lachuá) of the relatively flat lowlands of the Chixoy watershed and therefore will
likely exhibit a distinct microclimate. On the other hand, Lachuá vegetation is located
close to the Sierra Chamá foothills (~170 masl) and therefore exposed to increased
moisture due to orographic effects on precipitation. My climate data were unable to
capture this climatic variability likely because of the lack of spatial coverage of
meteorological stations in this region.
The climatic uniqueness of the Sierra Chinajá and Lachuá has resulted in the presence of
some plant taxa distributed normally in higher elevations at the Montane Cloud Forest.
Cloud forest microclimate and niche variability has possibly allowed highland species to
establish at locations outside of their expected distributional range, in this case in lower
elevations (Table 2.4). These species are found jointly in Chinajá and Lachuá, both at the
foothills of Sierra Chamá.
2.4.2 Watershed topography and landscape position
The other Montane Cloud Forest sites (Purulhá and Chelemhá) are most likely
differentiated in terms of their location in different mountain ranges: the Sierra Chuacús
and Sierra Yalijux, respectively (Figure 1.2). The low altitude mountain passes (valleys)
found between Purulhá and Chelemhá may function as a modern-day physical barrier for
49
biological dispersal as montane species would have to migrate below the minimum
altitude defining cloud forests (~ 400-1400 masl) to reach to the other side. Alternatively,
these valley bottom habitats act as corridors for biota that have adapted physiological
tolerances to lower elevation conditions (Schmitt et al., 2010). I believe the separation of
Tinajas 6 site from the other highland sites (Purulhá, Chelemhá) is probably due to the
fact that the site's vegetation data are based solely on forest inventories that lack
taxonomic specificity. In other words, the underlying explanation for the Tinajas 6 site
containing mostly generalist taxa (Billia hippocastanum, Dendropanax leptopodus) for
Lower Montane Rain Forest and Montane Cloud Forest is most likely a reflection of
differences in sampling intensity.
Analysis of sites as a function of their watershed location indicates that the landscape
position of sampling sites with respect to local relief (topography) may be another
important element in explaining plant community composition in the Guatemalan
lowlands. The Lachuá and Chinajá Lowland Rain Forest sites are more probably
differentiated from their lowland counterpart, Tinajas, because the former sites are found
in the Chixoy watershed and the latter in the Polochic watershed (Figure 2.1). These two
watersheds are separated by steep highland mountains, the Sierra Chamá and the east
portions of Sierra Yalijux. Steep mountain divides may be currently acting as physical
barriers to species migrations between adjacent watersheds. Janzen (1967) was the first to
recognize the ecological importance of steep elevational (climatic) gradients that tend to
be more common in tropical mountain passes than they are in mountainous regions at
higher latitudes (i.e. temperate and boreal regions).
50
DCA results indicate that longitudinal differentiation between western and eastern groups
in the Lower Montane Rain Forest correlate in part to topographical differences (Figure
1.2) and according to national descriptive maps (i.e. topographic and climatic), they may
also correlate to variations in temperature and precipitation (MAGA, 2004). The latter
response could not be tested due to the limitations of my climatic database. In the western
group, topography is influenced most by the narrow and higher elevation valleys at the
Cahabón watershed. In the eastern group, topography is characterized as wider and lower
elevated valleys located in the Polochic Watershed. The HCA dendrogram indicates that
although the Tamahú site is located in the eastern group, because of its geographical
proximity to the border of the Cahabón watershed, its vegetation is more similar to the
western group’s vegetation community than to that of the eastern group (i.e. an indication
of spatial autocorrelation).
2.4.3 Paleogeography and current vegetation biogeography
Analyses of data also indicate a possible role for biogeographic origin in explaining
vegetation distribution (Figure 2.4). Amazonian-centered taxa found in Central America
occupy ecologically important niches as lowland forest dominants with wide-ranging
distributions, and Andean-centered taxa dominate the humid foothills and mid-elevational
ranges (Gentry, 1982). Laurasian taxa are important in ecological terms because they are
dominant canopy members in montane forests, becoming more dominant as elevation
increases (Hammel and Zamora, 1990). In southeastern Mexico, Laurasian taxa were
found to increase with elevation, likely as a result of adaptations to climate-related
51
disturbances such as the risk of night frosts and desiccation arising from strong winds
(Quintana-Ascencio and González-Espinosa, 1993).
At this time, however, I believe it is premature to speculate on modern-day vegetation
trends in the Las Verapaces region (e.g. Amazonian, Andean, and Laurasian) or in the
rest of Guatemala arising from paleoclimate-forest dynamics. Glacial and inter-glacial
cycles of the Pleistocene are known to cause mixing of lowland and highland plant taxa
(Hooghiemstra and Van der Hammen, 2004), as well as to create a deterrent (barrier) to
vegetation migration between two points on the landscape (Terrab et al., 2008). Both
mixing and separation of plant taxa during the Pleistocene could explain the present
vegetation pattern found in the Las Verapaces elevational gradient (Figure 2.4). Studies
on the population dynamics of Scarabaeoidea (dung beetles) in Guatemala have identified
locations within montane cloud forests containing endemics that likely resulted from
Pleistocene paleoclimatology (Schuster, 2006). Because the delineation of Scarabaoidea
communities as a function of elevation (Schuster et al., 2000) is very similar to my
proposed vegetation belts, it makes the connection to Pleistocene dynamics all that more
enticing. Strong similarities and redundancy between flora and fauna distributions are
good indications of the importance of historical biogeographic processes in explaining
modern-day species distributions (Jones and Kennedy, 2008)
The regional geological history of Guatemala as it relates to mountain building in North
and South America may contribute to the explanation of why I have found a combination
of plant taxa with different biogeographic origins occupying different ecological niches
52
(Figure 2.4). Laurasian taxa typical of high elevation locations, for example, are found in
highland sites (Sauraia belisensis, Clethra suaveolens). For the most part, generalized
vegetation patterns across Central America were laid down in the Miocene period, when
Nuclear Central America was known as Proto-Central America (Raven and Axelrod,
1974; Graham, 1999). Orogenic processes in eastern-southern Mexico and central-
southern Guatemala (Padilla, 2007) likely promoted dispersion of Laurasian taxa
throughout the newly originated Guatemalan highlands. Amazonian-centered taxa
(Spondias mombin, Tabebuia sp.) dispersed into lowland regions via "island hopping"
over the Proto-Antillean Mountain Chain, both before and after the Pliocene closing of
the Central American Land Bridge approximately 3 million years ago (My). The physical
connection of Central America to South America also facilitated migration of Andean-
centered taxa (Oreopanax liebmanii, Weinmannia pinnata) into the foothills and
highlands in Guatemala where they currently dominate in the Montane Cloud Forest
(Table 2.3). Migration of Andean-centered taxa occurred sometime after Andean
orogenesis, beginning around 5 My BP (Antonelli et al., 2009).
2.4.4 Conservation biology and disjunctive taxa
Montane cloud forests are quickly becoming the focus of international conservation as
both their ecological and societal services are now being highly recognized (Vargas-
Rodríguez et al., 2010). Already, indications that cloud forests are experiencing change,
whether due directly to humans via land-use change or indirectly through climate change,
have been identified in India (Murugan et al., 2009), Mexico (Martínez et al., 2009) and
Central America (Colwell et al., 2008). Models predict that deforestation of lowland
53
rainforest causes a lowering of cloud base heights, in turn promoting reductions in
atmospheric moisture in the upper reaches of cloud forest (Nair et al., 2003). From a
conservation perspective, this study containing lists of plant species composition in
Guatemalan cloud forests will be important; as it is important to know what species are
there now so to have a benchmark from which to ascertain potential species turnover in
the future. The fact that some Montane Cloud Forest taxa have been observed at lower
altitudes in Purulhá and Chelemhá indicate that Chinajá and Lachuá forests have unique
habitat conditions (i.e. canopy microclimate) that have provided a critical refuge for
cloud forest plant species.
Andean-centered forest taxa such as Clidemia capitellata (Melastomataceae), Conyza
bonariensis (Asteraceae), and Dendropanax arboreus (Araliaceae) that are typically
located in the montane cloud forests were also found in lowland rain forests, indicating an
important link between both vegetation belts. Other taxa along our montane Chinajá site
also include non-plant taxonomic groups such as dung beetles, birds and bats (Bonham,
2006). In some cases the disjunctive pattern that we observed in understory vegetation
such as Lasiacis divaricata is more likely the result of insufficient sampling size due
mostly to the fact that the forestry surveys were primarily focused on canopy tree species.
Some Amazon-centered plant taxa from the Lauraceae (e.g. Ocotea and Phoebe) family
have extended their distribution from typical lowland habitats to high elevation
conditions (Chanderbali et al., 2001). Mixing of species increases regional diversity (i.e.
gamma diversity) as a response to the presence of multiple habitats (i.e. alpha and beta
54
diversity) each with unique physiographic and ecological features (Emmerson et al.,
2001).
2.5. Chapter summary
In this chapter three vegetation belts have been identified as expected and described in
terms of changes in plant communities along elevation. Other factors were found to
complementarily explain the relationship plant taxa-elevation, such as variability in
climatic parameters (i.e. temperature related), watershed location and topography, and
biogeographic origin. A list of 794 angiosperm plan taxa was generated based on the
collation of a data base of local vegetation inventories in the Las Verapaces region. This
list contains information about the elevation distribution of each taxon in different
watersheds according to the location of the vegetation inventory.
Based on a Detrended Correspondence Analysis (DCA), plant taxa with unique scores
along ordination Axis 1 were separated according to their distribution in elevation ranges
that corresponded three vegetation belts: Lowland Rain Forest (170-1000 masl), Lower
Montane Rain Forest (1000-1800 masl), and Montane Cloud Forest (1800-2500 masl).
The selection of these plant taxa is useful in identifying indicators for each vegetation
belt, or for generalists with a wider elevational distribution preference over no more two
neighbouring vegetation belts (Tables 2.3 and 2.4).
The application of identifying the correspondence between vegetation belts and indicators
and generalist taxa, is to know how to identify in calibration and paleoecological studies
55
the vegetation source of correspondent pollen taxa. Relating the prevalence of different
biogeographic origins (Amazonian, Andean, and Laurasian) and plant taxa provides the
linkage to understand the ecological characteristics of vegetation belts, which explains to
great extent the pollen source area and representations of pollen spectra of a location (i.e.
dispersion of pollen depends greatly on dispersal syndromes). In this sense Tables 2.3
and 2.4 are linked to Table 3.1.
56
Chapter 3:
Modern pollen rain in the north-central Guatemalan lowlands and highlands
3.1 Introduction
The correlation of modern pollen rain to landscape features is an important first step in
understanding the interpretation of paleoecological pollen signals at either local or
regional scales. Defined mostly from Northern Hemisphere paleoecological studies,
pollen observed in mid-sized to larger lakes represents mostly regional vegetation,
whereas pollen in observed in small basins represents local vegetation. As landscapes
become more open in character, the pollen signal from both smaller and larger basins
becomes more similar (Conedera et al., 2006; Lynch, 1996; Prentice, 1985). Thus, basin
size, range of pollen dispersal, and patterns of vegetation cover are factors that can
influence the mix of pollen found at any one sampling location. Moreover, other factors
such as topography, atmospheric conditions (i.e. prevailing wind circulation),
sedimentation rates and mode of sediment transport (Brown et al., 2008; Bunting et al.,
2004) may also control the mix of accumulating pollen.
In temperate regions (i.e. mid-latitude) it has been found that pollen content from
sediments of open basins has a more regional vegetation signal than a local signal,
because the pollen source area allows more deposition of wind-dispersed pollen (Fægri
57
and Iversen, 1989). Higher proportions of local vegetation have has been found in pollen
collected in forest interior surfaces, such as bryophyte polsters (i.e. moss polsters), where
short-distance dispersed pollen (i.e. animal pollinated) is found in greater amounts. Pollen
dispersal syndrome directly influences pollen source area and indirectly influences the
way pollen grains are trapped in different habitats and reservoirs (Bush and Rivera,
1998). The probability that bryophyte polsters will trap airborne pollen is low relative to
sediment samples from mid- and large-sized basins, where the effectiveness of vegetation
barriers decreases as distance increases from the shoreline (Conedera et al., 2006; Fægri
and Iversen, 1989; Lynch, 1996). Therefore, pollen content is different according to the
pollen sources, and in this case pollen signal of bryophyte polsters may indicate which
local pollen types are absent from surface sediments (Wilmshurst and McGlone, 2005).
This is of special interest for calibration because surface sediments represent the best
analogue for samples collected from cores where fossil assemblages are extracted from
and from where landscape evolution is inferred.
The over-arching objectives in conducting this research are two-fold: (1) To quantify the
relationship between modern pollen rain and local-to-regional features of the natural
landscape in two sites along a north-to-south elevational gradient (i.e. 170 to ~ 2000
masl) in the Las Verapaces region in Central Guatemala (Figure 3.1). The two sites are
located at the Lachuá lowlands and Purulhá highlands, in the Lowland Rain Forest belt,
and the Lower Montane Rain Forest-Montane Cloud Forest ecotone, respectively (see
Chapter 2). The Las Verapaces region was chosen because of its complex mosaic of
biophysical settings (Avendaño et al., 2007, MAGA, 2001) and archaeological sites
58
Figure 3.1. Location of Guatemala in Central America. Las Verapaces Region is enclosed in rectangle. 1= Lachuá lowlands, 2= Purulhá highlands.
MéxicoBelize
Honduras
NicaraguaEl Salvador
Costa Rica
Panama
Guatemala
Pacific Ocean
Caribbean Sea
Gulf of Mexico1
2México
Belize
Honduras
NicaraguaEl Salvador
Costa Rica
Panama
Guatemala
Pacific Ocean
Caribbean Sea
Gulf of Mexico1
2
59
(Dillon, 1977; Ichon et al., 1996). (2) To provide much-needed data for the Las
Verapaces region, an area that to date is under-explored in terms of modern pollen
calibration and paleoecology relative to the number of studies focusing on the northern
Guatemalan lowlands (Binford and Leyden, 1987; Curtis et al., 1996; Hillesheim et al.,
2005; Wahl et al., 2007a). This study represents the second modern pollen rain
calibration conducted in Guatemala and is one of the few studies in the Mesoamerica
region across Southeast Mexico, Guatemala, Belize and Honduras. For these reasons, this
study represents an important contribution for paleoecological study of tropical
ecosystems in general.
Specifically, I address the following three research questions: (1) What are the
differences between pollen spectra represented in bryophyte polsters and surface
sediments? How does the first inform me about the latter? (2) Is the modern pollen rain in
bryophyte polsters and surface sediments representative of local or regional vegetation?
(3) Which pollen taxa are reliable indicators of environmental conditions or vegetation
zonation along the study gradient?
3.2 Methods
3.2.1 Bryophyte polster pollen sampling
Bryophyte polsters were collected in the interior of minimally-disturbed forest habitats,
located far enough inside the forest (more than 250 m) to avoid “edge-effects” (Bush and
Rivera, 1998). Bryophyte polster samples from Lachuá lowlands (hereafter just Lachuá)
60
were taken every 50 m along a 200 m transect in two locations in the interior of forests
(n=10) (elevation ~170 masl) (interior of LLNP) (Figure 1.3). Bryophyte polsters
samples from Purulhá highlands (hereafter just Purulhá) were collected along a 2 km
transect (10 samples spaced 200 m apart) (elevation ~1700-1800 masl) (interior of
BUCQ) (Figure 1.3). A bryophyte polster sample comprised of the amalgamation of
bryophytes cushions found in a 5 m radius, were stored and labeled in plastic Ziploc bags.
3.2.2 Surface sediment pollen sampling
Surface sediments samples of 1.0 cm in length were extracted from cores taken using a
Livingstone corer and stored in plastic Ziploc bags. Lachuá samples are from Lachuá
Lake and Tortugas Ponds; and Purulhá samples from Chichoj Lake and the Cahabón
River Floodplain. Surface sediments from Lachuá samples were collected in three
locations (L1, L2 and L3) near the Lachuá lakeshore because the ideal location (lake
centre) was too deep to core (200 m) (Figure 1.3). I chose sites that were located away
from stream inflow and outflows to minimize disturbance of sediments. Sample L1 was
located approximately 2-3 m from the shore, sample L2 approximately 20 m from the
shore, and sample L3 was located in a lakeside wetland. Approximately 5 km northeast
from Lachuá Lake one extra core was sampled from the Tortugas Ponds shore at Salinas
de los Nueve Cerros Regional Park (sample Sa2). The pond is about 200 m in diameter
and is completely surrounded by high canopy (40 m) lowland rainforest (Cajas, 2009).
Surface sediments from the Purulhá were sampled in several Fincas (Villa Trinidad,
Patal, and Chisiguan) along the floodplains (600 m to 1 km wide) of the headwaters of
61
the Cahabón River (elevation range 1450-1560 masl), close to the towns of Purulhá
(samples P1 and P4) and Tactic (sample T1) (Figure 1.3). Another sample was taken
from a marsh adjacent to the heavily-polluted Lake Chichoj (sample J1) (47.6 ha) near
the town of Santa Cruz Verapaz (elevation 1390 masl) (Sánchez, 1994). As much caution
as possible was taken in choosing samples from locations where disturbance from
incoming rivers, landslides, or human activities was at a minimum.
3.2.3 Identification of pollen source areas
Pollen source area is considered "local" when the plant is reported in the local vegetation
inventory, "regional" when the vegetation source is located in a neighboring elevational
vegetation belt, and is considered “extra-regional” when the plant is separated more than
one vegetation belt (Chapter 2). Since I do not have modern pollen rain samples from
the Lower Montane Rain Forest (intermediate vegetation belt between Lachuá and
Purulhá), Lachuá pollen is regional when found in Purulhá because in terms of pollen
signal I considered Lowland Rain Forest and Lower Montane Rain Forest closely related,
an assumption based on Domínguez-Vázquez et al. (2004) (See Chapter 2 for definition
of vegetation belts). Due to their biogeographical affinity, arboreal pollen taxa from
Lachuá are named tropical and from Purulhá they are considered temperate. In the case of
Abies and Alnus, I consider them extra-regional for Lachuá because their plant stands are
found two vegetational zones higher, but for Purulhá they are regional. In the case of the
widely distributed Pinus, it is an indicator of highland temperate vegetation, independent
of its lowland populations (P. caribea). In order to create Table 3.1, identified pollen
types corresponding to plant taxa listed in Tables 2.3 and 2.4 were automatically
62
assigned to one or two vegetation belts. When pollen types (i.e. genus) are not found in
the latter tables, their allocation to lowlands or highlands vegetation, or a vegetation belt
not covered in the Las Verapaces (i.e. due to its location in higher elevation) was based
on revision of Latin American pollen and vegetation literature (Gentry 1982, Marchant,
2002; Domínguez -Vázquez et al. 2004).
3.2.4 Modern pollen laboratory work
Samples for pollen analysis were processed under standardized acetolysis procedures to
remove organic matter and cellulose, as well as to concentrate pollen grains (Fægri and
Iversen, 1989). Pollen counting was completed on a 200 grain per sample basis when
possible, of which at least 100 pollen grains were from arboreal taxa. Pollen
concentration was calculated based on the addition of exotic Lycopodium clavatum spore
tablets. A total of ten bryophyte polsters and four surface sediments samples were
counted in each of Lachuá and Purulhá making a total of twenty (20) bryophyte polsters
and eight (8) surface sediment samples.
Pollen grain identification was done using regional and local pollen reference collections
obtained from Colombia (Hooghiemstra, 1984), Barro Colorado Island in Panama
(Roubik and Moreno, 1991), Lachuá (Barrientos, 2006) and generally for the Neotropics
(Bush and Weng, 2007). Pollen identification was aided by the Pollen Reference
Collection from the Neotropical Research Unit from the Department of Geography,
University of Leicester, England. Fixed slides were stored in the reference collection at
63
the Paleoecology Laboratory of the Department of Geography at the University of
Toronto (Canada).
3.2.5 Modern pollen rain statistical calibration
The pollen sum included arboreal and non-arboreal taxa, which were identified to family
and genus level. Unknowns, spores and aquatics (e.g. Cyperaceae) were not included in
the pollen sum (Fægri and Iversen, 1989) and their abundance was measured as a ratio in
relation to the total pollen sum calculated per sample. Arboreal pollen (AP) and non-
arboreal pollen (NAP) percentages were calculated per site and pollen reservoir
(bryophyte polster and surface sediment) to represent local landscape vegetation cover.
Additionally, for each sample the contribution of pollen provenance (i.e. local or
regional) and pollen dispersal syndrome were identified. Dispersal syndrome included the
following: (1) zoophilous (animal dispersed), (2) anemophilous (wind dispersed), and (3)
ambiphilous (combination of both).
For local analysis at each site, species abundance matrices were built to compare
bryophyte polsters and surface sediments. In contrast, for regional analysis a common
matrix based on shared taxa between sites was built. Detrended correspondence analysis
(DCA) was used to visualize samples according to similarity of their pollen assemblages
and their probable arrangement as a function of environmental gradients (Jongman et al.,
1995). Analysis was complemented with a factor analysis (FA) using Varimax rotation in
order to isolate pollen types (factors) that explain the largest amount of variance (with
minimal loss of information) (May, 1974). The pollen type’s scores over FA gradients
64
(named "factors") complemented the explanation of gradients found in DCA axes.
Summary pollen diagrams were plotted based on local and regional analyses. PC-Ord
(McCune and Mefford, 2006) and PAST (Hammer et al., 2001) were statistical packages
used for multivariate analysis, and C2 (Juggins, 2003) for building pollen diagrams.
Information on pollen dispersal syndrome per taxon was derived from local vegetation
studies (Ávila, 2004; Cajas, 2009; García, 1998).
3.3 Results
56 pollen types were identified at least to family and genus taxonomic level at the Las
Verapaces region (Table 3.1). Pollen types were compared to information presented in
Tables 2.2 and 2.3 in order to link them to corresponding vegetation belt(s). Plant
indicator taxa (Table 2.2) correspond to one vegetation belt because of their specificity,
while generalist taxa correspond to two belts (Table 2.3). Based on criteria found in
bibliographic revisions of Latin American pollen studies, some pollen types were
interpreted to represent in general “lowlands” (i.e. Sapotaceae) or “highlands” (i.e.
Urticaceae) vegetation, when they represented more vegetation belts (i.e. Lowland Humid
Forest, see Table 2.1) that the ones covered in the Las Verapaces region vegetation
chapter (Chapter 2), or in the case that the pollen type had a wide altitudinal range
distribution either in lowlands (i.e. Celtis) or highlands (i.e. Pinus). Pollen types from
vegetation belts not found in the Las Verapaces region were collected (see Table 2.1),
such as Abies from Montane Mixed Forest, and Alnus from Montane Mixed Forest and
Subalpine Forest belt.
65
Lachuá species richness is higher than Purulhá (45 pollen types versus 31), with a total of
20 pollen types shared between sites (Figure 3.2). Bryophyte polsters contain higher
arboreal pollen (AP) type richness than surface sediments at both locations.
3.3.1 Lachuá modern pollen spectra
AP content is dominant in both bryophyte polsters and surface sediments at Lachuá, and
with few exceptions, consists of mostly local provenance and zoophilous taxa (Figure 3.3
and Table 3.2). Once the over-represented Pinus is removed from the AP data matrix, the
DCA diagram shows a general separation between bryophyte polsters and surface
sediments along Axis 1, with the exception of surface sediment sample Sa2 which is
separated along Axis 2 (Figure 3.4). Sa2 is segregated from other surface sediment
samples because its pollen content has the highest abundances of local taxa (Bursera,
Psychotria, Spondias, and Trema) and has the only record of Inga for surface sediments.
Surface sediments are dominated by the local entomophilous Celtis and highland
anemophilous Pinus. Sample L2 has the higher abundances of the temperate highland
anemophilous Abies and Myrica, and is the only sample that contains local
entomophilous Mimosa. Surface sediments at L3 have the highest abundance of Ilex
(highland zoophilous taxon) and some local entomophilous taxa such as Myrtaceae,
Sapium, Solanaceae and Terminalia. The pollen assemblage in sample L1 is a mix of taxa
found at sites L2 and L3.
The dominant taxa in bryophyte polsters are the local entomophilous Solanaceae and
highland Pinus. Many local entomophilous taxa (e.g. Bombacaceae) are only found in
66
bryophyte polsters (although poorly represented at ~1%). Various local entomophilous
(Brosimum and Terminalia), local anemophilous (Alchornea) and anemophilous
temperate (Alnus, Pinus, and Quercus) taxa have a wide representation across both pollen
reservoirs.
Asteraceae is similarly distributed in bryophyte polsters and surface sediments; Poaceae
is more abundant in the former, and Zea is poorly represented in both (~1%) (Figure
3.3). Trilete spores are consistently more abundant in bryophyte polsters, while monolete
spores (with the exception of sample L3) and aquatic pollen are similarly represented
across both pollen reservoirs.
3.3.2 Purulhá modern pollen spectra
The AP fraction is higher than non-arboreal pollen (NAP) in bryophyte polsters, and local
and anemophilous pollen fractions are higher than regional and zoophilous in both
bryophyte polsters and surface sediments (Table 3.3). Local anemophilous Hedyosmum
and Quercus are the most abundant AP taxa and are highly represented in bryophyte
polsters (Figure 3.5). With respect to AP and NAP combinations, DCA analysis shows a
separation between bryophyte polsters and surface sediments along Axis 1 (Figure 3.6).
Some regional taxa are represented in both pollen reservoirs (e.g. highland Alnus, and
lowland Celtis). Local (Ilex) and lowland taxa (Alchornea and Myrsinaceae) are found
only in bryophyte polsters relative to surface sediments. Temperate taxa abundances,
such as Abies, Pinus and the local Myrica, are similar in representation between
bryophyte polsters and surface sediments. Sample N4 presents the highest abundance of
67
Cecropia. Most of lowland taxa (in particular, those with entomophilous dispersal
syndrome) were poorly represented in both polsters and surface samples in highlands.
Poaceae is the most abundant NAP type and is more abundantly represented in surface
sediments, while Asteraceae (second most abundant NAP type) is similarly represented in
both pollen reservoirs. Surface sediment sample P4 is the only sample where the
disturbance-related taxon, Alternanthera, is found. Trilete spores are more abundant in
bryophyte polsters, while monolete spores and aquatic pollen types are dominant in
surface sediments.
3.3.3 Las Verapaces regional modern pollen spectra
Fifteen AP and five NAP taxa are common in both Lachuá and Purulhá (Figure 3.2),
with most of these taxa having their highest relative abundance either where plant stands
are reported from local inventories, or according to their elevational range of distribution
(Table 3.1). When analyzing shared AP-types, there is a clear separation along DCA
Axis 1 between the bryophyte polsters of Lachuá and Purulhá. Surface sediments are
located in the middle of Axis 1 (with some separation along Axis 2) and slightly
separated according to their location (Figure 3.7). The exception to this includes samples
L1, Sa2, and P4 surface sediments that are placed closer to their polster counterparts.
Lachuá surface sediment (L3) and Purulhá bryophyte polster (N8) are isolated on Axis 2
because they have the highest values of Ilex, which is neither found in bryophyte polsters
at Lachuá or surface sediments at Purulhá. When surface sediments samples are
compared at both Lachuá and Purulhá, there is a clear segregation between lowlands and
Table 3.1. Pollen types and their % range in abundance for bryophyte polsters (BP) and surface sediments (SS). Information about vegetation belt, plant habit, pollen dispersal syndrome (DS), and biogeographic origin (Biogeo) is provided, partially based on Table 2.2 and 2.3 (Chapter 2). Z= Zoophilous, W= anemophilous, A= Ambophilous (Z and W). L-BP to H-SS include percent pollen abundances. L= Lachuá lowlands, H=Purulhá highlands. Plant habit codes: T=Tree, S=Shrub, H=Herb. Vegetation belt codes (see Table 2.1): LRF= Lowland Rain Forest, LMRF= Lower Montane Rain Forest, MCF= Montane Cloud Forest, MMF= Montane Mixed Forest, SAF= Sub-Alpine Forest, *= Undefined vegetation belt, ?= Unassigned origin.
Pollen taxa
Genus Family Vegetation belt
Habit
DS
Biogeo
L-BP
L-SS
H-BP
H-SS
Acacia Fabaceae Lowlands T-S Z AMZ 2.70 1.61 Alchornea Euphorbiaceae Lowlands T W AMZ 0.8-8.5 1.6-2.6 0.5-2.1 Anthurium Araceae Lowlands H Z AN 10.80 Araliaceae Lowlands S Z AN 0.9 1.60 Arecaceae Lowlands S Z AMZ 1.1-10.9 0.9-3.22 Bignoniaceae Lowlands T Z AMZ 0.8-1.8 Bombacaceae Lowlands T Z AMZ 0.7-1.6 Boraginaceae Lowlands S Z LAU 0.80 Brosimum Moraceae Lowlands T Z AMZ 5.2-20 1.6-4.2 0.6-3.6 Celtis Ulmaceae Lowlands T Z LAU 1.5-20.1 1.6-14.4 0.5-3.1 0.90 Combretaceae/Melastomataceae Lowlands T Z AMZ/AN 0.8-9.1 0.8-1.6 Euphorbiaceae Lowlands T A AMZ 0.9-1.6 1.2-2.6 Fabaceae Lowlands T Z AMZ 1.8-8.1 0.80 Mimosa Fabaceae Lowlands T Z AMZ 0.60 Malpighiaceae Lowlands T-S Z AMZ 1.42 Moraceae Lowlands T W AMZ 1.8-12.1 0.90 0.7-1.1
Myrsinaceae Lowlands T W AN 0.5-6.6
69
Table 3.1 continued.
Pollen taxa
Genus Family Vegetation belt
Habit
DS
Biogeo
L-BP
L-SS
H-BP
H-SS
Myrtaceae Lowlands T Z AN 1.10 4.80 Pachira Bombacaceae Lowlands T Z AMZ 0.8-1.5 Piper Piperaceae Lowlands S Z AMZ 0.9-4.2 0.8-5.3 Psychotria Rubiaceae Lowlands S Z AN 1.1-4.1 4.8-16.7 Rubiaceae Lowlands S Z AN 0.8-6 0.80 1.60 Salvia Lamiaceae Lowlands T-S Z LAU 2.70 Sapium Euphorbiaceae Lowlands T Z AMZ 0.8-0.9 6.50 Sapotaceae Lowlands T Z AMZ 0.8-16.4 0.6-1.7 Solanaceae Lowlands T-S Z AN 0.8-24.1 0.6-9.7 Trema Ulmaceae Lowlands T Z LAU 0.9-3.6 15.80 Ulmaceae Lowlands T W LAU 0.9 Verbenaceae Lowlands H Z ? 0.8-2.3 1.3-6.5 Spondias Anacardiaceae LRF T Z AMZ 0.7-2.3 6.10 Bursera Burseraceae LRF-LMRF T Z AMZ 0.9-3.3 11.40 0.9-1.3 Cecropia Cecropiaceae LRF-LMRF T W AMZ 0.9-8.1 2.50 0.5-56.4 Terminalia Combretaceae LRF-LMRF T Z AMZ 2.7-16.4 0.6-9.7 0.5-1.5 0.70
70
Table 3.1. continued. Pollen taxa Genus Family Vegetation belt H DS Biogeo L-BP L-SS H-BP H-SS
Inga Fabaceae LMRF T Z AMZ 0.7-3.4 2.60 Hedyosmum Chloranthaceae LMRF-MCF T W LAU 0.8-1.8 0.80 3.3-31.3 1.2-5.9 Myrica Myricaceae LMRF-MCF S W LAU 0.8-4.1 2.6-42 0.9-10 1.9-6.1
Quercus Fagaceae LMRF-MCF T W LAU 0.7-8.1 0.8-2.6 10.3-60.9 3.1-16.7
Abies Pinaceae MMF T W LAU 0.8-1.5 3.4-9.6 0.7-7 1.2-8.5 Alnus Betulaceae MMF-SAF T W LAU 1.7-9.9 0.6-4.2 0.8-2.2 1.2-1.3 Ericaceae Highlands S W AN 1.7-4.2 Conifer6 Pinaceae Highlands T W LAU 0.8 Pinales Pinaceae Highlands T W LAU 0.7-3.6 0.7 Pinus Pinaceae Highlands T W LAU 9-35.1 1.6-46.6 2.2-16.6 3.7-14.8 Urticaceae Highlands H W AN 2.20
71
Table 3.1 continued.
Pollen taxa
Genus Family
Vegetation belt
H
DS
Biogeo
L-BP
L-SS
H-BP
H-SS
Alternanthera Amaranthaceae * H Z ? 0.8-3.2 4.90 Amaranthaceae/Chenopodiaceae * H Z ? 0.9-1.7 0.80 0.5-0.9 0.6-1.3 Asteraceae * H Z AN 1.6-6.9 0.6-4.8 0.8-20.3 11.8-15.9
Cyperaceae * H AMZ 1.4-7.6 0.8-4.8 0.6-5.1 70.1-140.3
Peperomia Piperaceae * H Z AMZ 0.9-3.3 1.7-1.8 Piperaceae * S Z AMZ 0.6-2.6 0.7-0.9 Poaceae * H W ? 1.6-6.5 0.8-1.6 0.9-41.6 14.7-65.6 Polygonum Polygonaceae * H Z ? 1.4-24.5 Zea Poaceae * H W AMZ 0.8-0.9 1.70 0.5-0.9 0.7-1.9
Trilete spores * H ? 56.1-96.3
18.9-89.2
80.9-94.9 14.5-45.5
Monolete spores * H ? 3.7-43.9 10.8-81.1 5.1-19 54.5-85.5
72
CaCbCcCeCdRaRbRcReRd
Sa2L1L2L3P1P4T1J1N1N2N3N4N5N6N7N8N9
N10
BP Lachua
SS Lachua
SS Purulha
BP Purulha
0
Alchorn
ea
0 20
Brosim
um
0 20
Bursera
0 20 40 60
Cecrop
ia
0 20
Celtis
0 20
Morac
eae
0
Rubiac
eae
0 20
Termina
lia
0 20 40
Hedyo
smum
0 20
Ilex
0 20 40
Myrica
0 20 40 60
Quercu
s
0
Abies
0
Alnus
0 20 40
Pinus
12 36 60 84 108
AP
-0.2 0.2 0.5 0.8 1.1
FA1
Tropical trees and shrubs Temperate trees and shrubs
Figure 3.2. Pollen diagram from Lachuá and Purulhá based on bryophyte polster (BP) and surface sediment (SS) samples. Ca to Rd Lachuá BP, and Sa2 to L3 Lachuá SS. P1 to J1 Purulhá SS, and N1 to N10 Purulhá BP. + = rare taxa appearing at <1%. AP=Arboreal pollen, FA1=Factor Analysis first component.
Percent pollen abundance
73
CaCbCcCeCdRaRbRcReRd
Sa2L1L2L3P1P4T1J1N1N2N3N4N5N6N7N8N9
N10
BP Lachua
SS Lachua
SS Purulha
BP Purulha
0
Alterna
nthera
0
Amaranth
acea
e / C
heno
podia
ceae
0 20
Asterac
eae
0 20 40 60
Poace
ae
0
Zea
0 20 40 60
Trilete
0 20 40
Monole
te
0 30 60 90 120 150
Cypera
ceae
0 120 240 360 480 600
Pollen
conc
entra
tion (
x100
0 grai
ns/cm
3)
0 30 60 90
NAP
-0.2 0.2 0.5 0.8 1.1
FA1
Herbs Pteridophytes
Figure 3.2. Continued. NAP=Non-arboreal pollen, FA1=Factor Analysis first component.
Percent pollen/spore abundance
74
CaCbCcCeCdRaRbRcReRd
Sa2L1L2L3
BP
SS
0
Acacia
0
Alchorn
ea
0
Araliac
eae
0 20
Arecac
eae
0
Bignon
iacea
e
0
Bomba
cace
ae
0
Boragin
acea
e
0 20
Brosim
um
0 20
Bursera
0
Cecrop
ia
0 20
Celtis
0
Combre
tacea
e / M
elasto
matace
ae
0
Fabac
eae
0
Inga
0 20 40
Solana
ceae
0
Malpigh
iacea
e
0
Mimos
a
0 20
Morace
ae
0
Myrtac
eae
0
Pachir
a
0 20
Psych
otria
0
Rubiac
eae 1
0 20
Rubiac
eae 2
0
Salvia
0Sap
ium
0 20
Sapota
ceae
0
Spond
ias
0 20
Termina
lia
0 20
Trema
0
Conife
r 6
0
Hedyo
smum
0
Ericac
eae
0 20
Ilex
0 20 40
Myrica
0
Quercu
s
0
Abies
0
Alnus
0 20 40
Pinus
0 20 40 60 80 100
AP
-1.0 0.0 1.0 2.0 3.0
DCA 1
0.0 1.0 2.0 3.0
DCA1 (-P
inus)
Tropical trees and shrubs Temperate trees and shrubs
Figure 3.3. Lachuá pollen diagram based on bryophyte polster (BP) and surface sediment (SS) samples. + = rare taxa appearing at <1%.
Percent abundance
75
Ca
Cb
Cc
Ce
Cd
Ra
Rb
Rc
Re
Rd
Sa2
L1
L2
L3
BP
SS
0
Alterna
nthera
0
Ama/Che
n
0 20
Anthuri
um
0
Asterac
eae
0
Pepero
mia
0
Piper
0
Poace
ae
0
Verben
acea
e0
Zea0
Cypera
ceae
0 20 40
Trilete
0 20 40
Monole
te
0 16 32 48 64 80
Pollen
conc
entra
tion (
x100
0 grai
ns/cm
3)
0 4 8 12 16 20
NAP
Herbs Pteridophytes
Figure 3.3. Continued. AP=Arboreal pollen, NAP=Non-arboreal pollen, DCA1= Detrended Correspondence Analysis first axis.
Percent abundance
76
Samples AP NAP Local Highlands Z W
Ca 81 19 78 22 72 28Cb 100 0 84 16 78 22Cc 88 12 86 14 84 16Cd 96 4 72 28 68 32Ce 86 14 75 25 59 41Ra 94 6 77 23 68 32Rb 93 7 42 58 30 70Rc 90 10 59 41 50 50Rd 90 10 74 26 67 33Re 89 11 52 48 30 70
Sa2 92 8 85 15 66 34L1 91 9 38 62 34 66L2 98 2 56 44 56 44L3 87 13 74 26 70 30
Sample AP NAP Local Lowlands Highlands A W Z
N1 79 21 83 10 7 4 90 7N2 65 35 82 5 12 1 95 4N3 86 14 67 25 7 18 77 5N4 88 12 92 5 3 1 98 1N5 77 23 75 22 4 15 84 1N6 49 51 78 14 8 11 84 6N7 62 38 71 19 10 8 86 5N8 69 31 82 14 3 2 66 32N9 83 17 89 5 6 2 95 3N10 94 6 90 8 2 0 94 6
P1 26 74 55 15 30 10 85 5P4 41 59 86 5 10 0 95 5T1 18 82 79 7 14 7 93 0J1 38 62 72 6 22 4 94 2
Table 3.2. Lachuá bryophyte polsters (Ca-Re) and surface sediments (Sa2-L3) samples. Local and highlands (regional and extra-regional) refers to percentages of arboreal pollen (AP) spectra. NAP= Non-arboreal pollen, Z= Zoophilous, W=Anemophilous.
Table 3.3. Purulhá bryophyte polsters (N1-N10) and surface sediments (P1-J1) samples. Local, lowlands, and highlands refers to percentages of arboreal pollen (AP) spectra. NAP= Non-arboreal pollen, A=Ambophilous, Z= Zoophilous, W=Anemophilous.
77
Figure 3.4. Lachuá DCA Q-mode ordination diagrams of AP data with Pinus removal. (+) represent bryophyte polsters, and diamonds surface sediments.
78
N1
N2
N3
N4
N5
N6
N7
N8
N9
N10
P1
P4
T1
J1
BP
SS
0 20
Eupho
rbiac
eae
0 20 40
Hedyo
smum
0 20
Ilex
0
Myrica
0 20 40 60
Quercu
s
0
Urticac
eae
0 20
Pinus
0
Pinales
0
Abies
0
Alnus
0Alch
ornea
0
Brosim
um
0
Bursera
0 20 40 60
Cecrop
ia
0
Celtis
0
Morace
ae
0
Myrsina
ceae
0
Rubiac
eae
0
Termina
lia
0
Ulmac
eae
16 32 48 64 80 96
AP
0 100 200 300
DCA1
Temperate trees and shrubs Tropical trees and shrubs
Figure 3.5. Purulhá pollen diagram based on bryophyte polster (BP) and surface sediment (SS) samples. + = rare taxa appearing at <1%.
Percent abundance
79
N1
N2
N3
N4
N5
N6
N7
N8
N9
N10
P1
P4
T1
J1
BP
SS
0
Amaranth
acea
e / C
heno
podia
ceae
0 20
Asterac
eae
0
Piperac
eae?
0 20 40 60
Poace
ae
0
Zea
0 20
Polygo
num
0 30 60 90 120 150Cyp
erace
ae
0 20 40 60
Trilete
0 20 40
Monole
te
0 120 240 360 480 600
Pollen
conc
entra
tion (
x100
0 grai
ns/cm
3)
0 30 60 90
NAP
Herbs Aquatics Pteridophytes
Figure 3.5. Continued. AP=Arboreal pollen, NAP=Non-arboreal pollen, DCA1= Detrended Correspondence Analysis first axis.
Percent abundance
80
Figure 3.6. Purulhá DCA Q-mode ordination diagrams based on AP and NAP data. (+) represent bryophyte polsters, and diamonds surface sediments
81
and highlands pollen along DCA Axis 1.
At Lachuá, temperate Alnus and Pinus have high abundances in both pollen reservoirs.
Abies is similarly represented in surface sediments from Lachuá and Purulhá, and in
bryophyte polsters at Purulhá (Table 3.1). Highland taxa, Quercus and Hedyosmum, are
abundant in both bryophyte polsters and surface sediments at Purulhá. Pollen taxon
Myrica has similar abundances in Lachuá and Purulhá (both polsters and surface
sediments), with the exception of L2 where Myrica reaches its highest representation.
Cecropia plant stands are found in both Lachuá and Purulhá (i.e. indicator species for
disturbance-edge effects) and Cecropia pollen is over-represented in one sample of
bryophyte polsters at Purulhá.
Asteraceae and Poaceae taxa have their highest abundances at Purulhá. Poaceae pollen is
more abundant in surface sediments than in bryophyte polsters. At both Lachuá and
Purulhá, Amaranthaceae/Chenopodiaceae and Zea are rare (Table 3.1). Alternanthera has
similarly low abundances in Lachuá and Purulhá surface sediments. Trilete spores are
generally more abundant in bryophyte polsters of Lachuá and Purulhá like in surface
sediment samples of Lachuá. In contrast, monolete spores have their highest abundance
in Purulhá surface sediments. Aquatics (i.e. Cyperaceae) are likely over-represented
relative to the pollen types included in the pollen sum in surface sediments from Purulhá.
Results of factor analysis indicate pollen types that explain the maximum amount of
variance along positive and negative trends of the ordination gradients (Table 3.4). For
82
Lachuá, the variance in positive trend is explained by Pinus and Myrica; with the
negative variance trend explained by Solanaceae and Sapotaceae. The trend represented
by these groups of pollen taxa, correspond most likely the pollen source area, the former
highlands and the latter lowlands. Once Pinus (over-represented) is removed, the
following other pollen types explain the variation: (1) Celtis, Brosimum, Terminalia and
Sapotaceae along a positive trend, and (2) Ilex and Trema explains the negative trend. For
Purulhá, the main explanatory taxa are the following: Quercus and Ilex in a positive
trend, and Euphorbiaceae and Abies in a negative trend. These two trends in Purulhá may
indicate small scale gradients, because apparently they do not reveal an environmental
gradient between forest interior (e.g. bryophyte polster) and open landscape (i.e. surface
sediment). The main taxa for both Lachuá and Purulhá correspond to the lowlands to
highlands environmental gradient: Quercus, Hedyosmum, Asteraceae, and Cecropia
along a positive trend, and Celtis and Brosimum along a negative trend.
83
Figure 3.7. Las Verapaces DCA Q-mode diagram AP shared data. Lachuá surface sediments are indicated by circles, and bryophyte polster samples are enclosed by the continuous line polygon. Purulhá surface sediments are indicated by discontinuous line squares, and bryophyte polster samples are enclosed by the discontinuous line polygon. See tables 3.2. and 3.3 for codes.
84
Table 3.4. Factor Analysis scores for pollen types with highest amount of variance. + or – indicates direction of magnitude along factors. Location Taxon Factor 1 Factor 2 Factor 3
Brosimum
+2.4
Celtis +4.6
Lachuá
Terminalia +1.6 Sapotaceae +1.3 Solanaceae -5.7 Poaceae +6.9 Asteraceae +1.6
Quercus +4.3 Ilex +1.0
Purulhá
Euphorbiaceae -0.6 Abies -0.4 Myrica -2 Pinus -3.3 Cecropia +4.4
Quercus +5.4 Hedyosmum +4.1 Cecropia +1.1
Las Verapaces
Asteraceae +1.4 Pinus +6.0 Celtis +2.1 Brosimum +1.9 Ilex -1.0 Poaceae +6.9 Asteraceae +1.6 Hedyosmum -0.7
85
3.4 Discussion
3.4.1 Relevance of dispersal syndrome for pollen assemblages in bryophyte
polsters and surface sediment
Taxonomic content, which in turn is tightly correlated with dispersal syndrome and
pollen source area, contributes in differentiating bryophyte polsters and surface sediments
at both Lachuá and Purulhá (Tables 3.2 and 3.3). Because local plant taxa in Purulhá are
mostly temperate and therefore anemophilous (i.e. rich pollen producers), AP spectra are
almost entirely local. In an analysis of modern pollen rain where moss polsters were
collected in the same sites where vegetation cover was recorded using a Braun-Blanquet
scale in the Guatemalan western highlands (2800-3800 masl) and Volcanic Chain (3000-
4000 masl) (Islebe and Hooghiemstra, 1995), pollen spectra showed widespread over-
representation of anemophilous taxa (e.g. Pinus, Alnus, and Quercus). The explanation is
because at these elevations, anemophily is the dominant pollen dispersal syndrome.
Lachuá's AP spectra are more representative of local tropical provinces that contain more
zoophilous plant taxa (i.e. poor pollen producers). Islebe and Hooghiemstra (1995) found
that in spite that zoophilous pollen taxon poor abundance could under-estimate the local
abundance of the plant, their presence correspond well with the elevational vegetation
zone associated with the plant itself (e.g. Buddleja pollen found only in the subalpine
forest belt at 3400-4000 masl). This is probably because short-distance pollen dispersal
results in more accurate representation of local vegetation. Pollen taxa from highlands
still contribute in a major way to Lachuá pollen spectra, because highlands pollen is
largely more adapted for airbone dispersion than lowlands pollen. On the other hand,
86
representation of lowlands pollen taxa in highlands is minimal because of the poor
abilities of lowlands pollen for long-distance dispersal.
Regional analysis of Lachuá data indicates that bryophyte polsters and sediment samples,
L1 (close to lakeshore) and Sa2 (small basin), are similar in that they share at least some
percentage of local pollen (Figure 3.4). In general, pollen trapped in bryophyte polsters
travels shorter distances from within the surrounding forest (Fægri and Iversen, 1989),
and to a much lesser extent, traps pollen that is airborne (i.e. transported great distances)
or is the consequence of wind friction created by forest canopy gaps. Sediment sample
Sa2, was collected from a small basin surrounded by high canopy forest; therefore its
similarity in pollen signal to bryophyte polsters is not surprising because the surrounding
high canopy forest likely acted as a barrier to long-distance dispersal. Despite this, Sa2
shows partial separation from bryophyte polsters when the full AP spectrum is analyzed
(Figure 3.4). Lachuá vegetation analysis shows that the "landscape unit" (i.e.
homogeneous biological and geomorphological area) where Sa2 is located (Salinas de los
Nueve Cerros) is different due to its unusual hilly topography within the generally flat
landscape of Lachuá. Landscape topography has been shown to influence composition of
vegetation communities (Cajas, 2009) and therefore to influence pollen source.
Even though surface sediments samples were not collected from the exact center of the
Lachuá Lake (i.e. ideal sampling location), their long-distance dispersed AP content is
sufficient to produce a typical highland signal (15-62%). Local analysis of Lachuá shows
a clear separation of both pollen reservoirs once the over-represented Pinus is removed
87
(Figure 3.4). As with many regions world-wide, Pinus is notorious for overshadowing
signals from local pollen taxa (for discussion about Pinus pollen see section 3.4.5).
Because Purulhá’s surface sediments were collected in mid-sized basins located in
deforested landscapes, pollen spectra would be expected to have a major regional pollen
content (Sugita et al., 1999). Nevertheless, because zoophilous pollen dispersal syndrome
dominates, Purulhá’s regional component from the lowland is minimal (zoophilous; 5-
15%) and mostly local (anemophilous; 55-86%) (Table 3.2). The higher content of
lowlands pollen in bryophyte polsters in comparison to surface sediments could be
explained in terms of differential preservation. Forest interior conditions where bryophyte
polsters are found allow for better preservation of pollen (i.e. less dessication under a
canopy cover) (Vermoere et al., 2000). Surface sediments from the small basin Chichoj
Lake and Cahabón river floodplain correspond to lentic (still water ecosystem) and lotic
(flowing water ecosystem) environments, respectively (Brown et al., 2007), yet
surprisingly their pollen spectra shows a degree of similarity (Figure 3.6). The similarity
in pollen collection in lentic and lotic environments is likely due to the energy
environments in which the sediments were deposited (i.e. both are low energy
floodplains). In addition, their location within a deforested landscape results in overall
low AP values.
3.4.2 Influence of land-use change on pollen source
Deforestation rates are currently high in Purulhá highlands, thus the expected high AP
sediment signal in basins and lakes surrounded by forest is not possible to be assessed
88
(e.g. no forest surrounds any possible sediment reservoir candidate for paleoecological
research). Despite this limitation, forested conditions should be identified if pollen
spectra from sedimentary records are similar to modern pollen spectra from bryophyte
polsters (i.e. high AP values). Other studies in tropical highlands with other types of
reservoirs have differentiated between forest, grasslands, and open spaces based on
different pollen spectra and associated forest taxa contribution (Kennedy et al., 2005;
Olivera et al., 2009).
From Quintana Roo in Mexico, Islebe et al. (2001) analyzed pollen rain from moss
polsters along a disturbance gradient which included lowland forest, disturbed forest, and
secondary vegetation. The pollen data provided a clear signal for the three vegetation
types because they cover large areas in the region, and a list of 15 indicator taxa was
selected based on their overall good representation in the pollen spectra. In contrast,
bryophyte polsters and surface sediments from Lachuá reflect the local forested condition
because of their high AP values (14,500 ha of forest on Lachuá Lake National Park),
which is similar to other lowland pollen analyses in the tropics where forest cover
conditions are similar (Behling and Negrelle, 2006; Batthacharya et al. 2011). In contrast,
Dominguez-Vásquez et al. (2004) found a dominant allochtonous (i.e. anemophilous)
signal in the Lacandon Lowland Rain Forest in Chiapas, Mexico. A greater allochtonous
contribution in the Lacandon lowlands pollen spectra may be a response to higher
deforestation rates, because as openness increases in landscapes long-distance dispersed
pollen input increases (Lynch, 1996; Gaillard et al., 2008; Hellman et al., 2009), which in
the case of lowlands scenarios correspond to highlands anemophilous pollen taxa.
89
3.4.3 Tropical and extra-tropical generalities
The present study and others (Bush and Rivera, 1998; Bush and Rivera, 1991) indicate
that it is not possible to generalize pollen differences in bryophyte polsters from surface
sediments in tropical regions like it is done for northern temperate and boreal latitudes
(Bush, 1995). In extra-tropical climates of the Northern Hemisphere, generalizations
concerning the primary presence of short-distance dispersed pollen in bryophyte polsters
and long-distance dispersed pollen in surface sediments are acceptable (Fægri and
Iversen, 1989). Tropical environments are completely different because dispersal
syndrome is more important than basin-size generalizations in long- and short-distance
dispersal. In tropical lowland environments, for example, short-distance dispersed pollen
refers mainly to zoophilous taxa, whereas long-distance dispersed pollen mainly to
anemophilous pollen. In contrast, in tropical highland environments short-distance
dispersed pollen (i.e. local input) will contain anemophilous pollen. Long-distance
dispersed pollen (i.e. regional input) in tropical highland environments will contain
pollen from both anemophilous pollen from higher elevations and lowland zoophilous
taxa (although not aerodynamically designed, some are transported by upslope winds).
Elevational gradients in the tropics do not conform to generalities made for northern
temperate regions (Janzen, 1967).
In three out of four existing modern pollen rain studies for the Maya region (Islebe and
Hooghiemstra, 1995; Islebe et al., 2001; Domínguez-Vázquez et al., 2004), pollen is
captured by moss polsters in different scenarios, lowland and highland settings, and all
contain an over-representation of long-distance dispersed taxa (anemophilous taxa) and
90
an under-representation of short-distance dispersed taxa (mostly entomophilous taxa).
This in turn interfered with the overall ability to detect typical "regional" versus "local"
vegetation signals. Broadly-dispersed tropical and temperate anemophilous taxa in
tropical regions, such as the Amazon Forest, reflect a less heterogeneous and diverse
landscape. This relationship poses a limitation to differentiating ecosystem types in the
pollen record (Bush et al., 2001). To overcome difficulties associated with anemophilous
taxa, Gosling et al. (2009) have stressed that more attention should be placed on
identifying and differentiating pollen abundances and accumulation rates for ecosystems.
Nonetheless, to achieve this it requires extensive spatial and detailed temporal sampling.
3.4.4 Identifying indicator taxa and vegetation associations
The pollen collection sites represented changes along the elevational gradient from
Lachuá to Purulhá (Figure 3.7 and Table 3.4), as has been found in other pollen studies
in Latin America (Weng et al., 2004; Weng et al., 2007). For their study region in
Guatemala, Islebe and Hooghiemstra (1995) concluded that moisture gradients have an
important role in explaining variation in pollen assemblages. In an elevational gradient
(from 130 to 1191 masl) in the Chiapas Lacandon Forest in Mexico, modern pollen
spectra collected from moss polsters (Domínguez-Vázquez et al., 2004) indicate high
overlapping of lowland rain forest and lower montane rain forest vegetation zones, and
montane rain forest and pine-oak forest respectively. The majority of pollen types from
Lachuá and Purulhá are generalist since they represent mainly lowlands and highlands
vegetation, while few represent a specific vegetation belt (Table 3.1). This representation
pattern in the Las Verapaces region is similar to the analysis of Dominguez-Vásquez et
91
al. (2004), which indicates that pollen taxa represent broader and less specific
environmental ranges, possibly in response to the taxonomic resolution of genus and
family. According to results from Chapter 2 (Table 2.2 and 2.3) a few pollen types can
be associated to specific vegetation belts, such as the case of Spondias for Lowland Rain
Forest, and Inga for Lower Montane Rain Forest, and although not part of the Las
Verapaces Region, Abies for Mixed Montane Rain Forest. In a smaller spatial scale,
Batthacharya et al. (2011) were able to differentiate lowlands ecosystem types (i.e.
upland, bajo, and riparian forests) in Northeast Belize based on changes in abundance of
pollen types in relationship to ecological preferences of the correspondent source plant
taxa.
Gradients interpreted from DCA Axes and factor analysis identify indicator taxa for
Lachuá and Purulhá. Pollen from Celtis is associated with Lowland Rainforest in both
pollen reservoirs and is known to indicate high canopy transition (medium- to large-size
trees) in an early- to mid-succession phase following human disturbance (Marchant et al.,
2002). In Guatemala, plant stands of C. trinervia have been recorded in Lowland Humid
Forest from the Petén (Standley and Steyermark, 1946), an area which receives less
precipitation than the Lachuá Lowland Rain Forest (Standley, 1958). Celtis has thus
adapted to drier conditions and therefore could be found from lowland vegetation up to
lower montane rain forest. Such a trend has already been reported in pollen studies from
Costa Rica (Islebe and Hooghiemstra, 1997). The large tree, Brosimum has similar
distribution preferences as Celtis plant stands because it too has been reported in Lowland
92
Humid Forest (Cascante and Estrada, 2001) (see Table 2.1) and Lowlands Rain Forest
(Chapter 2), such as the lowland rain forests from Lachuá (Table 3.1).
Terminalia pollen is a generalist taxon characteristic of Lowland Rain Forest and Lower
Montane Rain Forest (Chapter 2). I also identify Sapotaceae pollen as representative of
Lachuá Lowland Rain Forest, an observation similarly made in other areas of Latin
America (Marchant et al., 2002). In my study, both Hedyosmum and Quercus indicate
Lower Montane Rain Forest and Montane Cloud Forest vegetation, a distribution also
found elsewhere in the tropics (Domínguez-Vázquez et al., 2004). At Purulhá, the values
of these two taxa are lower in surface sediments than in bryophyte polsters most likely
because of proximity of forest stands to polsters and because in surface sediments, values
are diluted by high abundance of non-arboreal pollen (NAP).
The abundance of Quercus in bryophyte polsters (10-61%) is higher than those recorded
by Islebe and Hooghiemstra (1995) (3-16%), whom sampled at higher elevations (above
3000 masl) where oak is naturally less abundant (i.e. too cold). Pollen abundances of
Hedyosmum found in bryophyte polsters in the present study (3-31%) are similar to
values documented by a study in southern Peru (15-65%), at elevations between 1600-
2000 masl (Weng et al., 2004). In contrast, Islebe and Hooghiemstra (1995) did not find
Hedyosmum pollen at higher elevations (> 3000 masl) in Guatemala. Islebe and
Hooghiemstra (1995) found relatively high concentrations of Abies and Alnus at
elevations higher than 3000 masl (30 and 40%, respectively) yet I report a maximum
abundance of 10% for both because of their relative absence in forests in my study region
93
(Chapter 2). Ilex pollen appears to be behaving as an outlier, because it is unclear why
this zoophilous highland taxon is as abundant in Lachuá’s surface sediments as in
Purulhá’s bryophyte polsters, and yet is totally absent in Purulhá’s surface sediments.
Differential preservation could in part explain this seemingly odd distribution, but the
explanatory mechanism remains speculative. According to Behling et al. (1999), the
ecological significance of finding Ilex within a paleoecological context remains uncertain.
Analysis of pollen in bryophyte polsters and surface sediments aided in identifying
indicator and generalist plant taxa at Las Verapaces region, showing partially the results
from the inventory study of vegetation belts (Chapter 2). Lowland taxa such as Bursera,
Inga, Spondias and Trema, and highland taxon such as Myrica, are reported in current
forest inventories (Chapter 2) but they are not statistically relevant in the ordination
gradients formed for DCA and Factor Analysis based on pollen in this study.
Nevertheless, they are qualitatively key taxa whose importance remains in their
associated presence-absence in the pollen spectra. Weng et al. (2004) have suggested that
in order to maximize detecting environmental changes for tropical studies qualitative
information such as presence/absence data should become more prominent in
palynological studies.
3.4.5 Interpretation of Pinus pollen
Overrepresentation of Pinus taxon is discussed separately because its abundance has to be
read carefully due to its high dispersion ability (Bohrerova et al., 2009). The location of
the sampling point is therefore critical to understand what Pinus pollen percentages
94
reflect. Pinus is more abundant in bryophyte polsters and surface sediments from Lachuá
than from Purulhá possibly because of a mixture of pollen sources from different
populations of Pinus species (Figure 3.2). Natural Pinus populations are established in
different highland regions around Lachuá, in the northwest at the Chiapas highlands of La
Selva Lacandona (Breedlove, 1981), in the west and southwest at the Sierra de los
Cuchumatanes (Islebe et al., 1995), and Pinus caribea populations north of Lachuá and to
the northeast in Belize (Bridgewater et al., 2006). Pinus pollen has been considered as an
indicator of highlands vegetation where abundances can reach up to 90-95% (above 2500
masl) which inform me more about larger scale scenarios (i.e. across different regions)
(Islebe and Hooghiemstra, 1995).
Nevertheless, as was found in Chapter 5, Pinus pollen percentages of the last ca. 2000
yrs in Lachuá lowlands have never been as abundant as modern pollen rain analysis
shows. High abundance of Pinus pollen in Lachuá may represent the general increasing
environmental deterioration of Mesoamerican forests in Southeast Mexico and
Guatemala, because it is known that Pinus is a successful colonizer of disturbed areas. A
related factor to be considered is the extensive Pinus plantations established in lowlands
and highlands in the recent years in Guatemala as part of governmental reforestation
programs (Gaillard, 2003). This probably created a bias in the modern pollen rain
(Behling and Negrelle, 2006), which urges the necessity to develop more modern pollen
rain studies in the region. A recent study by Battacharya (2011) in a pine savanna
(characterized by the presence of Pinus caribea and Quercus) shows similar Pinus pollen
95
percentages to the ones found in Lachuá (up to ca. 40%), which possibly explains how
Pinus pollen could reflect local Pinus populations.
One factor that currently precludes geographical discrimination of pollen provenance of
Pinus populations is that highland Pinus species and P. caribea pollen cannot be
differentiated because they form part of the same subgenus (i.e. Diploxylon). More
palynological work with Pinus and other pollen types (e.g. Combretaceae and
Melastomataceae) is required to overcome these taxonomic limitations in order to
identify more accurately pollen source areas, geographical provenance, and ecological
preferences.
3.5. Chapter summary
The purpose of modern pollen rain calibrations developed in this chapter is to understand
better the meaning of the pollen spectra of surface sediments, as they represent the best
analogue for sedimentary records. Calibrations of modern pollen rain of bryophyte
polsters and surface sediments from Lachuá lowlands and Purulhá highlands revealed the
importance of geographical context and related vegetation. Results from Chapter 2 were
the basis to determine pollen source areas of pollen types found in modern pollen
reservoirs, as Table 3.1 indicates. The pollen assemblage in Lachuá lowlands is
dominantly zoophilous because the associated vegetation is mainly of tropical
biogeographic origin (Amazonian and Andean). This is the reason why lowlands pollen is
poorly represented in the highlands pollen assemblage, because zoophilous pollen taxa
96
disperse mostly over short distances. On the contrary, because the pollen assemblage in
Purulhá highlands is dominantly anemophilous (adapted for airborne dispersal) and of
temperate biogeographic origin (Laurasian), they are relatively more abundant in the
Lachuá lowlands pollen assemblage.
In general terms, surface sediments in Lachuá lowlands have similar pollen spectra than
the one found in bryophyte polsters, with the exception that the latter contained higher
abundances of forest interior taxa (e.g. Brosimum, Celtis, and Terminalia) and some
additional taxa (e.g. Bignoniaceae and Salvia). In the Lachuá lowlands, in both types of
depositional environments (polsters and surface sediments), high arboreal pollen content
was linked to the high remaining forest cover of the area (ca. 50%). In Purulhá
highlands, bryophyte polsters and surface sediments pollen spectra are different due to
the fact that the former were collected in forested conditions (e.g. high percentages of
Hedyosmum and Quercus), and the latter in a more open landscape. The non-arboreal
pollen content of bryophyte polsters and surface sediments reflected the degree of forest
cover where pollen reservoirs were collected, low for the former and high for the latter.
Combined analysis of pollen spectra of Lachuá and Purulhá showed the clearest
elevational differentiation when comparing bryophyte polsters, and lesser when
comparing surface sediments. The explanation for this pattern could be that surface
sediments from Lachuá lowlands have a significant representation of highland pollen,
which needs careful attention when interpreting fossil pollen spectra.
97
The application of modern pollen rain calibration from bryophyte polsters and surface
sediments is developed in the following chapters on the paleoecology of Lachuá lowlands
and Purulhá highlands. Data matrices of modern pollen rain from both types of pollen
reservoirs are compared with fossil pollen assemblages from different levels in the cores
L-3 in Lachuá lowlands and P-4 in Purulhá highlands. These comparisons are the basis
for determining analog or non-analog environmental conditions along the temporal frame
covered in each core. Pollen types included in Table 4.4 were relevant in developing
paleoecological reconstructions in Chapter 4 and Chapter 5. The contributions of
Chapter 2 and Chapter 3 in understanding the importance of the relationships between
geographical context, vegetation biogeography, environmental conditions, and pollen
spectra resulted in better interpretations of the paleoecology of Lachuá lowlands and
Purulhá highlands.
98
Chapter 4:
Late-Holocene History of a Highland Floodplain in Las Verapaces, Guatemala
4.1 Introduction
Sedimentary records from lakes and peat deposits are one of the most relied upon tools
for paleoecological research, in part because aquatic environments are generally more
stable (i.e. continuous accumulation through time) and less disturbed than riverine
environments (Larsen and Macdonald, 1993; Birks, 2005; Brown et al., 2007). In
circumstances where lacustrine and peat deposits are rare, records from floodplains,
terraces and alluvial fans have been instead studied (Cheng, 2011; Gandouin et al., 2006;
Gandouin and Ponel, 2010). Paleoenvironmental information retrieved from river
floodplains can reflect in some cases floodplain communities, and to a lesser degree
upland vegetation communities (Solomon et al., 1982; Xia et al., 2002; Zazula et al.,
2006). Regional pollen however, is generally represented in floodplain sedimentary cores
(Qinghai et al., 1996). Floodplain sedimentary records offer a unique opportunity to study
the paleoecology of high energy systems (i.e. riparian plant communities) as well as their
successional dynamics related to flood events (Pokorny et al., 2000) and disturbances
such as fire (Gagnon, 2009).
It was the objective of my study to retrieve fossil pollen spectra from the headwaters of
the Cahabón River floodplain in the Las Verapaces highlands region of central
Guatemala (Figure 1.2 and 1.3). Due to the dominant karstic geology of the Las
99
Verapaces region (Fourcade et al., 1999), aquatic ecosystems are mostly dominated by
sinkholes or “cenotes” where sediments are minimal to non-existent. Only a few small
lakes have been reported in the region as most have been either naturally drained through
karstic bedrock or anthropogenically disturbed (Castañeda, 1995). This study represents
the first paleoecological study (spanning the past ~2,400 years) of a region located in a
floodplain environment in highland Mesoamerica. Archaeological studies indicate the
existence of numerous small Maya centers in the Las Verapaces (i.e. Carcha, Sakajut,
Chican, Pasmolon) (Arnauld, 1978; Arnauld, 1987; Arnauld, 1997; Sharer and Sedat,
1987) that date from the Pre-Classic through to the Spanish Conquest.
The research goals of the following study are twofold: (1) to reconstruct the
paleoenvironmental history of a river floodplain located in the Las Verapaces highlands
for the past ~2400 years, with methods based on pollen and loss-on-ignition (LOI)
analysis, and (2) to make regional comparisons between other records in Mesoamerica,
with special emphasis on highland ecosystems. This research builds on previous highland
studies of vegetation biogeography (Chapter 2) and modern pollen calibrations
(Chapter 3).
4.2 Methods
4.2.1 Core Sampling and Laboratory Work
With the use of a Livingstone Corer, I extracted a ~1.5 m core (labeled as P-4) on the
north side of the Cahabón River headwaters floodplain (Figure 1.3). The location of my
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core was cautiously selected in order to avoid any disturbance from modern hydrological
modifications on the Cahabón River floodplain, landslides on the slopes or incoming or
outflowing rivers. Coring was stopped once it became impossible to continue due to
stiffness of sediments.
The top centimeter of P-4 core was separated for modern pollen rain calibration (Chapter
3), and the rest was wrapped in aluminum foil and enclosed in a PVC pipe. A 1 ml sub-
sample was taken every 5 cm along P-4 core. Sub-samples were stored in Ziploc bags,
and the core’s stratigraphy was qualitatively described. After proper labeling, the core
and the subsamples were stored in a cold room.
According to the Department of Geography Protocol (No. 010) of the University of
Leicester, samples were pre-treated overnight with pyrophosphate, followed by standard
acetolysis procedure and heavy liquid separation with the use of bromoform (Fægri and
Iversen, 1989). Exotic Lycopodium spore tablets were added as markers to calculate
pollen concentration. Pollen counting was completed to 200 grains per sample when
possible (Lytle and Wahl, 2005). Pollen sum included arboreal and non-arboreal taxa that
were identified to family and genus level. Unknowns, spores and aquatics (Cyperaceae)
were not included in the pollen sum (Fægri and Iversen, 1989) and their abundance was
measured as a ratio in relationship to the total pollen sum per sample.
Arboreal pollen (AP) and non-arboreal pollen (NAP) percentages were calculated to
represent local landscape vegetation cover. The Loss of ignition (LOI) protocol used at
101
the Paleoecology Laboratory of the University of Toronto (Heiri et al., 2001) was applied
for each subsample where pollen was analyzed (see above), to calculate the organic
(550°C), inorganic (950°C), and silicate (% left) contribution to the sediment sample
(estimated 2% error in the measurement). Only the LOI at 550°C is presented and
referred as "LOI". A bulk sample from the bottom level (145 cm in depth) of core P-4
(Purulhá) was radiocarbon dated to estimate the time span of the core, and three
additional samples (25, 50 and 70 cm in depth) were dated to develop models of sediment
accumulation rates. Dates were calibrated through the use of the IntCal04 curve from
CALIB 6.0 (Stuiver et al., 2005).
4.2.2 Core data analysis
Pollen counts were tabulated for pollen types and core levels (sub-samples), including for
the surficial level, for comparison with the modern pollen rain data presented in Chapter
3. Arboreal and non-arboreal pollen types were included in the pollen sum, excluding
aquatics (e.g. Cyperaceae), pteridophytes spores, and unknowns. For pollen
concentration, all counts were included. Principal component analysis (PCA) (Shi, 1993)
was performed with the statistical package PAST (Hammer et al., 2001) to describe
changes of pollen spectra along the core including common and rare taxa (Figure 4.3). A
second PCA was done (Figure 4.6) for the comparison of fossil pollen spectra of sampled
levels of the P-4 core and modern pollen spectra from bryophyte polsters and surface
sediments from Purulhá highlands (Chapter 3). The software C2 (Juggins, 2003) was
used to construct a stratigraphic diagram (based on depth measured in cm and calibrated
time scale) (Figure 4.1) according to the information on vegetation belts and pollen types
102
presented in Table 3.1. Vegetation belts included in Figure 4.1 are Lower Montane Rain
Forest-Montane Cloud Forest and Mixed Montane Forest (see Table 2.1 and Table 3.1),
which comprised the sum of the percentages of Hedyosmum, Myrica and Quercus; and
Abies and Alnus, respectively. Complementary information for stratigraphic diagrams
(Figure 4.1 and 4.4), included relative abundance of arboreal (temperate trees and
shrubs) and non-arboreal pollen content, aquatics, pteridophytes spores, LOI (loss-on-
igition), sedimentation rate, and PCA axes scores. The stratigraphic diagram was divided
into a priori zones according to cultural periods defined for Mesoamerica (i.e. see
Introduction, section 1.7).
Equations for sedimentation rates were calculated based on sediment thickness (in cm)
per number of years between two identified dates. An analysis based on nine regional
studies from Mexico and Central America and our data spanning the Preclassic to
colonial times (Almeida et al., 2005; Carrillo-Bastos et al., 2010a; Conserva and Byrne,
2002; Dull et al., 2010; Figueroa-Rangel et al., 2008; Islebe and Hooghiemstra, 1997;
McNeil et al., 2010; Wahl et al., 2006) was performed to compare our calculated
sedimentation rates with values found in other Mesoamerican highland and lowland sites.
A total of 65 levels (radiocarbon dates) from the nine sites were included in my analysis,
which were allocated into elevation and cultural period categories. The sites used in this
regional comparison were placed into groups according to elevation: 0-500 m (n=20),
500-1000 m (n=16), 1000-2000 m (n=9), and 2000-3100 m (n=20); and cultural periods:
Preclassic (n=26), Classic (n=10), Postclassic (n=13), and Colony (n=3). Levels that
cover Pleistocene (n=4) and Archaic times (n=9) (5000-10000 yrs BP) were excluded
103
from my analysis. Based on non-parametric boxplots (Tukey, 1977; Hyndman and Shang,
2010), P-4 sedimentation rate values were plotted in order to explore if they behaved as
outlier values for the groups were they belonged. The analysis was complemented with a
Kruskal-Walis test to test the coherence of created elevation and cultural period groups
(Kruskal and Wallis, 1952). P-4 sedimentation rate values are located in the 1000-2000 m
ranges, and across four cultural periods (Preclassic, Classic, Postclassic, European
conquest and Colonial Guatemala).
4.3 Results
4.3.1 Stratigraphical description
The P-4 sediment core is characterized by an alternation of different tones of gray fine
grained sediment from the base at 144 cm up to 30 cm in depth (Table 4.1). Brown fine
grained sediment are found in between 30 and 5 cm depths, and dark brown organic
matter in the top 5 cm. LOI values steadily increase from 9 to 13% between the Late-
Preclassic and Late-Classic period (144-45 cm in depth) (Figure 4.1). At the time of the
Terminal Classic and onset of the Postclassic, there is a decrease in LOI to 9% (45-40 cm
core interval). A two-fold increase in LOI to 16% occurs during the next 300 years; LOI
values remain high (15-22 %,) during the Colonial to present-day cultural period.
4.3.2 Chronological control and sedimentation rates
The oldest age of 2390 yrs BP (all ages are reported as calibrated years before 1950 AD)
corresponds to sediments at the bottom of the core (144 cm in depth). Subsequent
104
radiocarbon analyses indicate ages of 2060 yrs BP at 70 cm, 1510 yrs BP at 50 cm, and
150 yrs BP at 25 cm (Figure 4.2) (Table 4.2). There are two critical inflection points in
the age-depth curve, at 70 cm of depth, and above 25 cm of depth (Figure 4.2).
According to such a pattern, different periods of changing sedimentation rates (i.e.
changing of energy at time of deposition, sediment type, or source area) can be
postulated.
The lower phase from 2390 yrs BP until 2060 yrs BP (144-70 cm core interval) records a
relatively rapid sedimentation rate of 0.22 cm yr-1 (corresponding cultural period of the
Late Preclassic to Terminal Preclassic). The next phase, which includes dates from 2060
until 1510 yrs BP (70-50 cm core interval), has a marked reduction in sedimentation rate
to 0.036 cm yr-1 (corresponding cultural period of the late Preclassic to the middle
Classic). The following phase includes dates from 1510 until ~150 yrs BP (50-25 cm core
interval) and has an even more marked reduction in sedimentation rate to 0.018 cm yr-1
(corresponding cultural period of the middle Classic to end of the Postclassic, and the
start of Colonial Guatemala). The upper phase, from ~150 yrs BP to modern-day (25-0
cm core interval) shows a relative increase in sedimentation rate to 0.17 cm yr-1 (cultural
period of Colonial Guatemala).
The sedimentation rates found for P-4 core (0.22, 0.036, 0.018, and 0.17 cm yr-1) are not
outliers in the groups they belonged according to elevation and age (Figure 4.3). There is
no statistically significant difference in rate of sediment accumulation among the sites in
the regional comparison when they are divided by cultural period (Kruskal-Walis H=,
105
p>0.01); and in relation to elevation, ranges 500-1000 and 1000-2000 m ranges are
considered a group, and 0-500 and 2000-3100 m another group (Kruskal-Walis H= 32.87,
p<0.01). The exploration of sedimentation patterns and differences in relationship to
environmental and cultural factors needs further discussion in the future, but is beyond
the scope of this thesis.
4.3.3 Description of pollen diagram
The variability found along the first factor of principal component analysis (PCA1) and
the first component of factor analysis (F1) (Figure 4.1), corresponds to the pollen zones
that were identified a priori based on cultural periods. According to trends in the PCA
Axis 1 analysis, the main variability in pollen assemblages occurs as a function of
changes in abundance of Asteraceae (Figure 4.4). PCA Axis 2 scores are linked to
variation in the dominances of Pinus and Alternanthera, Quercus, Poaceae and
Polygonum, alternating with dominance of Amaranthaceae/Chenopodiaceae (Figure 4.4).
The presented pollen diagram (Figure 4.5) is based on common and rare taxa identified
to at least to the level of genus or family. Tropical lowlands pollen taxa are extremely
rare and do not show a clear trend in the P-4 core. Pollen zones were closely related to the
four cultural periods identified to our region: Pre-Classic, Classic, Post-Classic, Colonial
and modern-day Guatemala. For the core interval between 144 and 90 cm (representing
the period from 2390 to 2150 yrs BP) there was no pollen or spore preservation.
106
Table 4.1. P-4 core stratigraphic sequence.
Stratigraphy of core P-4 taken from the Cahabón Floodplain, Purulhá Depth (cm)
Description
0-5 5-30 30-32 32-39 39-44 44-49 49-86 86-93 93-105 105-111 111-119 119-144
Dark brown organic material Light brown organic material Dark gray fine grained sediment Medium gray fine grained sediment Bright gray fine grained sediment Medium gray fine grained sediment with oxide (red) spots Brown-greyish fine grained sediment Dark gray fine grained sediment Medium gray fine grained sediment Dark gray fine grained sediment Bright gray fine grained sediment Bright grey-green fine grained sediment with black laminations
Table 4.2. AMS radiocarbon dates, calibrates age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá highlands. Bold numbers in brackets are the calibrated dates. All radiocarbon dated material is from bulk samples.
Depth (cm)
Lab No
13C/12C
14C yrs BP
Age range 2σ and Median Age (in
brackets) (cal yrs BP)
25
Beta-281243
-24.6
150±40
42-(151)-284
50
Beta-281244
24.3
1510±40
1313-(1394)-1517
70
Beta-281245
-24.3
2060±40
1926-(2029)-2133
144
GrA-40112
---
2390±35
2341 –(2422)- 2683
107
Zone 1: Pre-Classic (2390-1650 yrs BP)
Pollen is preserved starting at 2150 yrs BP (90 cm). This zone is characterized by a
dominance of non-arboreal pollen (78-90%) consisting mostly of Asteraceae (48-76%);
with Asteraceae remaining at high values (55%) until the end of the Postclassic. Other
non-arboreal taxa include Poaceae (1-17%), Amaranthaceae/Chenopodiaceae (4-21%)
and Zea (1-3%) which remain at relatively low to medium values throughout the zone.
Cyperaceae (27-80%), Polygonum (0-4%), trilete spores (6-23%) and Monolete spores
(0-14%) all reach their minimum values in this zone. Pinus is present at intermediate
values (3-11%), similar to Hedyosmum (0-6%) and Quercus (1-8%), with Myrica
reaching its maximum abundance (0-5%) in the entire core. Regional taxa for the
modern-day Cahabón floodplain, Abies and Alnus, are not present at this time.
Zone 2: Classic (1650-1240 yrs BP)
This zone has relatively decreasing pollen abundances of Pinus (4-6%), Hedyosmum (1-
3%), Myrica (0-3%) and Quercus (0-4%). Alnus (1%) and Malphigiaceae (2%) make
their first appearance along the core. Non-arboreal pollen dominates this zone (87-89%),
once again consisting mainly of Asteraceae (46-71%). In comparison to Zone 1, Poaceae
(6-29%), Polygonum (0-9%), Cyperaceae (60-165%), and trilete spores (9-48%) increase
in abundance, while Amaranthaceae/Chenopodiaceae (4-9%) decrease. Zea (0-4%) and
monoletes spores (4-17%) have similar values across Zone 1 and Zone 2.
108
Zone 3: Post-Classic (1240-420 yrs BP)
Total arboreal pollen shows a subtle decrease to between 5 and 13%; comprising mainly
Pinus (2%), Hedyosmum (2-6%), Quercus (1-2%), Alnus (0-1%) and Malphigiaceae
(1%). Myrica is absent. Similar to Zone 2, Asteraceae is the dominant taxon (55-56%)
showing only small variations in concentration between the zones. Other taxa that show
small decreases in concentration include Poaceae (4-16%), whereas Cyperaceae (19-
20%) decreases the most substantially. Amaranthaceae/Chenopodiaceae (1-25%), trilete
spores (22-112%) and monolete spores (47-97%) all show an increase in abundance.
Polygonum (3-5%) and Zea (3-5%) abundance remains the same across the previous zone
to Zone 3.
Zone 4: Colonial to modern-day Guatemala (420 yrs BP-Present)
This zone is characterized by a co-dominance of Pinus and Asteraceae with maximum
values at 30 and 35%, respectively. It is only at the most recent time that Pinus shows a
modest decrease (to 12%). In general, Quercus shows stability with low values (~1%)
along most of the core. Whereas Pinus shows decrease in the uppermost sample, Quercus
shows an abrupt increase (18%). Abies (modern-day regional species; Chapter 4) appears
for the first time in this zone, with a trend towards increasing abundance through time
(i.e. from 0 to 4% by the top of the core). The observed three-fold increase in arboreal
pollen (from between 10-22% to between 32-49%) is due to increased presence of Pinus,
Quercus and Abies. Hedyosmum shows relatively stable presence (2-7%) at the start of
the zone, and then begins to decrease (2%) towards the modern-day time. Myrica (0-3%)
109
and Alnus (0-1%) show a similar pattern where their populations are relatively stable in
the lower sections of the core, then begin to decrease towards the upper part of the core.
By the onset of Colonial Guatemala, Asteraceae begins to show a sharp drop in
dominance (17-36%) showing even a lesser value at the present (13%) (Chapter 3). Zone
4 shows Cyperaceae increasing to its maximum value (from 49 to 226%), followed by a
sharp decrease to (58%) in the upper-most sample. In contrast, Polygonum shows a
steady and gradual increase (2-17%) until the modern day (26%). Poaceae shows an
increase in abudance to its peak (4-26%) during this zone, but right at present day, the
abundance of Poaceae returns to values more characteristic of previous zones (16%).
Amaranthaceae/Chenopodiaceae shows small decreases (3-13%) towards present day, a
pattern also observed for trilete spores (10-36%) and monolete spores (10-32%). At the
start of Zone 4, Zea abundance begins to decrease (0-1%) but then begins to recover (2%)
near present day. The most significant pollen signal in this zone is the first appearance of
the disturbance indicator, Alternanthera (1 - 11%). According to the PCA ordination
(Figure 4.4), the major division in the core in terms of the pollen assemblages is between
the Guatemala zone and pre-Guatemala zones.
110
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Depth
(cm)
Guatemala
Postclassic
Classic
Preclassic
0 20 40
Pinus
0 20
LMRF-M
CF
0
Mixed M
ontan
e Fore
st
0 20 40 60 80 100
Herbs
0 10 20 30 40 50
AP
0 4 8 12 16
Pollen
conc
entrati
on (x
1000 g
rains
/cm3)
0 8 16 24
LOI 5
50
0.0 0.1 0.2 0.3
Sed. r
ate (c
m/yr)
-80 0 80 160
PCA 1
100
350600850
110013501600
1850
2100
2350
Cal yrs
BP
Figure 4.1. P-4 core paleoecological diagram taken from Cahabón River Flooplain. AP = Arboreal pollen; LOI550 = Loss on ignition at 550°C (expressed as % of dry mass); PCA1 = Axis 1 scores from principal components analysis. Sedimentation rate is shown in cm/yr. Mayan cultural periods are shown. The Guatemala zone represents modern day Republic of Guatemala. Vegetation belts are composed of pollen indicator taxa (see Table 3.1 and section 2.4.3 for calculations). LMRF= Lower Montane Rain Forest, MCF= Montane Cloud Forest.
Percent abundance
111
Depth (cm)
0 20 40 60 80 100 120 140
Cal
enda
r age
(cal
yr B
P)
0
500
1000
1500
2000
2500
Figure 4.2. Graph showing depth (cm) vs. calendar age (cal yrs BP) of sediments from core P-4 taken from the Cahabón River floodplain, as determined by 4 radiocarbon dates (black diamond symbols, see Table 4.2). Asymmetric bars indicate ±2σ in cal. yrs.
112
Figure 4.3. Sedimentation rate (cm/yr) values from elevation ranges (masl) across Mesoamerica, as determined from a regional comparison from nine published studies (65 radiocarbon samples). Small squares= outliers.
113
Modern
G5
G4
G3
G2
G1
PT3
PT2PT1
C4
C3C2
C1PC6
PC5
PC4PC3
PC2
PC1
-32 -16 16
PCA1
-20
-10
10
PC
A2
Figure 4.4. Principal Component Analysis (PCA) of sampled levels from core P-4. PCA1= First principal component, PCA2= second principal component. PC= preclassic levels, C=classic levels, PT=postclassic levels, G= Guatemala zone, modern= surface sediment (0-1 cm) for core P-4.
114
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Depth
(cm)
Guatemala
Postclassic
Classic
Preclassic
Arecac
eae
Hedyo
smum
Ilex
Malphig
iacea
e
Myrica
20
Quercu
s
20 40
Pinus
Abies
Alnus
20 40 60 80
Asterac
eae
20
Amaranth
acea
e /Che
nopo
diace
ae20
Poace
ae
20Alte
rnanth
eraZea Alch
ornea
Brosim
umBurs
eraCelt
isCom
bretac
eae /
Mela
stomata
ceae
Myrtac
eae
0 20
Polygo
num
0 50 100 150 200 250
Cyper
acea
e
0 30 60 90 120
Trilete
0 24 48 72
Monole
te
0 20 40
AP
100
350600850
110013501600
1850
2100
2350
Cal yrs
BP
Temperate trees and shrubs Herbs Tropical trees and shrubs Aquatics Pteridophytes
Figure 4.5. Pollen percentage diagram of P-4 core from the Cahabón River floodplain. Rare taxa appearing at <1% are indicated by a "+" symbol. .
Percent abundance
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4.4 Discussion
4.4.1 Ancient lacustrine-like conditions at the floodplain?
The development of the Cahabón River Floodplain at 2390 yr BP is characterized by a
relatively higher sedimentation rate than in the present, which based on other studies in
similar types of settings, could mean a higher energy regime related to fluvio-lacustrine
(river to lake transition) environments (Figure 4.1). A range of 5-9% for LOI during this
time period (2390 until 2170 yrs BP) at P-4 core is similar to what was recorded in the
environments of a paleolake that once existed in the basin of Bogota from the late-
Pliocene through the Pleistocene (Torres et al., 2005). LOI values around 10% found in
lacustrine conditions indicate the provenance of the sediments mainly from swampy
environments. It is possible that core P-4 is located at what was once a swamp (i.e. light
gray fine grained sediments) in the remnants of a lacustrine environment (Shuman, 2003).
The location of core P-4 corresponds to the headwaters of the Cahabón River watershed,
at the top of a plateau where the drainage divide is located (Figure 4.6). The relatively
flat terrain and the location of the floodplain are factors that may help explain the
existence of a paleolake, but nevertheless particle size analysis is needed to permit more
conclusive inferences. The fine grained sediments suggest a location with low energy
and not close to a main channel where sediments are in general coarse-grained (Bridge,
2003). In the Bogota Basin swamp environments with fine grained sediment in a fluvio-
lacustrine hydrological context with LOI values from around 10% (Torres et al., 2005),
are interpreted as episodes of high rates of bioturbation due to high levels of biological
activity in organic-rich mud. This in turn may help to explain the absence of pollen
grains observed in our P-4 core during this time (144 to 90 cm) as a result of bioturbation
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disturbance. Further exploration about the possible existence of formerly paleolacustrine
conditions in the floodplain is needed (e.g. particle size analysis), because our speculation
is greatly based only on the Torres et al. (2005) study.
An alternative explanation for the absence of palynomorphs in the lower section of the
core could be that this was a period of rapid sedimentation due to increased erosion or
flows in the river, either due to natural (e.g. higher precipitation due to a wetter climate,
or any other related hydrological changes) or cultural factors (e.g. increased erosion due
to deforestation), preventing in the end the accummulation and deposition of pollen and
spores into the sediments. The absence of palynomorphs in the lower section of the core
makes it difficult to infer what the vegetation cover could have been during this time
period (2390 until 2150 yrs BP). Although differences exist, sedimentation rates from the
bottom (Preclassic period) and the top (Guatemala zone) belong to higher ranges (0.22
and 0.17 cm yr-1), which suggests that sedimentary conditions may have been relatively
similar. In this area today, economic human activities have resulted in a high
deforestation rate leaving most of the floodplain valley floor and slopes with scarce
vegetation cover (MAGA, 2006). By analogy, the same low vegetation cover could be
inferred for the beginning of our core; however, there is insufficient evidence to indicate
whether or not the cause of low vegetation cover was due to natural or cultural
circumstances. Nevertheless, a cultural cause may help explain the high sedimentation
rate caused from slope erosion into the floodplain (Thieme, 2001; Charlton, 2008). The
first Preclassic agriculturalists in Mesoamerica have been associated with evidence of the
highest rates of soil erosion and degradation in the region, mainly due to the
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VP
CH
CX
SL
P‐4
Figure 4.6. Cahabón River Floodplain. The core P-4 is located in the headwaters of the Cahabón River (running eastwards). Rivers are irregular black thick lines. Dark grey polygons represent natural reserves (mainly Montane Cloud Forest). Archaeological sites are indicated by circles: VP= Valparaiso, CH= Chican, CX= Cerro Xucaneb, SL=Sulin. See Figure 1.4 for elevation references.
118
trial and error of people learning the consequences of land-use change (Beach et al.,
2006).
The lower-most pollen sample in the P-4 core (at 90 cm) shows a low percentage of
arboreal pollen and high values of herbs. The bottom of P-4 core could be indicating
intense land use change and conversion to agricultural uses (e.g. Zea and Cyperaceae).
The inferred lacustrine swampy environment was probably disturbed at this time, as a
slight increase in LOI (9 to 13%) possibly represent land use modifications in the
floodplain. The fact that pollen appears simultaneously strengthens the possibility that
LOI increase is due to the floodplain stabilization.
4.4.2 Evolution of Mayan land management at the Cahabón Floodplain
The accompanying changes in fluvial parameters may have been influenced by
(culturally-induced) hydraulic management of the floodplain (i.e. leading to the presence
of fine-grained sediments that are darkin in colour and higher in organic matter) (Table
4.1, see interval 49-86 cm). Approximately 340 years after the first appearance of pollen
in P-4 core (2040 yrs BP), the sedimentation rate decreases several-fold (from 0.22 to
0.036 cm yr-1), possibly indicating that early Mayans evolved along this time some form
of soil conservation practice that helped to decrease rates of soil erosion. It is possible
then that progressive agriculturally-related fallow debris may have increasingly
influenced the slight increase of LOI from 9 to 13% during those three centuries. Changes
in PCA1 values suggest that vegetation dynamics reflect approximately the conditions in
the riparian zone before the sedimentation rate decreased, in between the end of the
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Preclassic and start of the Classic (Figure 4.1). For many years, archaeologists have
shown evidence that the early Mayans incorporated terraces and raised fields in their
agricultural management plans, ultimately leading to reduced soil erosion over the time
the region was in agricultural use (Beach, 2003; Beach et al., 2009). Raised fields were
useful in modulating soil-water conditions, where channels in between the field
functioned to regulate water tables resulting in permanent flooded conditions (e.g. rise in
water table) (Turner and Harrison, 1981; Scarborough, 1991; Beach et al., 2011). The
sedimentation rate in core P-4 remained relatively low for roughly 1600 years (e.g. from
0.036 to 0.018 cm yr-1), until the end of the Postclassic period, when presumably
dispersion of Mayan populations resulted in abandonment of established agricultural
plots.
Arboreal components (Hedyosmum, Myrica, and Quercus) from Lower Montane Rain
Forest (i.e. located most likely along the valley bottom) and Montane Cloud Forest (i.e.
located most likely along the valley slopes) may be an indication of recovery from
agricultural disturbance, since their presence in the floodplain environment increases
towards the late-Preclassic (i.e. rising 3 to 11%). The first appearance of Zea pollen
during the late-Preclassic with values lower than 1% supports the development of
agriculture in the floodplain, because generally Zea pollen disperses close to its source
(McNeil et al., 2010). Progressive increment in Zea pollen percentages greater than 1%
suggest possibly that agriculture was developing in a wider area along the floodplain and
more intensively, as has been reported in other Mesoamerican locations (Wahl et al.,
2007). Currently the major land use at the floodplain is cattle pasture with some
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agricultural plots (personal observation). This is reflected in modern pollen rain (Chapter
3) where values of Zea pollen are higher in surface sediments (>1%) than in bryophyte
polsters (<1%) (Figure 3.5), because the latter were collected in forest interiors far away
from the floodplain (ca. 5 km). PCA ordination of modern and fossil AP pollen spectra
shows how bryophyte polsters do not overlap with sediments over PCA1, while modern
surface sediments overlap with Preclassic, Classic, and Postclassic sediments because
possibly the landscape was similar in openness (Figure 4.7). Analysis of multiple cores
along the study site (e.g. Cahabón Catchment) will in the future allow a more complete
view of the evolution of the floodplain.
Present day AP values range from 16 to 32% which corresponds to the current deforested
and open landscape at the Cahabón River Floodplain, but with scattered forest remnants
in the valley slopes (Figure 3.5 and Figure 4.8). In comparison the 11% arboreal content
at the late-Preclassic could be signalling even less presence of continuous forest cover,
and more open shrubland near the floodplain, most likely on valley slope environments.
Pollen abundance below 5% for Myrica throughout the core supports this hypothesis (van
der Hammen and Hooghiemstra, 2003). Approximately 90 ky yrs BP, higher abundance
pollen values (around 30%) at Lake Fuquene in Colombia indicate the presence of
Myrica shrub forest surrounding the lake. In the Las Verapaces region today at
elevational ranges from ~1400-2000 masl, Myrica pollen is an indicator of open
landscapes and humid grounds (Marchant et al., 2002) (i.e. 2-6% in surface sediments,
see Chapter 3) which are similar to the values observed during the Preclassic (i.e. 1-4%).
In west-central Mexico today, montane forest taxon Quercus has remained non-dominant
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in the pollen record, even when it has maintained a stable presence during fully-forested
conditions (Figueroa et al. 2008), but in this case, the presence of Myrica pollen
throughout the core supports a more open structure vegetation.
The existence of an open environment during the late-Preclassic is highly supported by
the presence of Asteraceae pollen, a disturbance-related family of vegetation. Asteraceae
pollen dominates the floodplain until the end of the Postclassic when agriculture ceased.
Other pollen taxa that indicate localized disturbance include Amaranthaceae
/Chenopodiaceae and Poaceae. The latter pollen types have opposing patterns of
maximum values (r = -0.52 p = 0.02), possibly related to different phases of post-
agricultural vegetation succession. Present day Poaceae pollen has greater values in the
floodplain (16 to 66%) than in the past (3 to 28%), evidence for the current major land
use as pasture lands (e.g. grasses). Lower present day values of Asteraceae (<16%),
support the idea that land use was different in the past (e.g. agriculture) (Figure 3.5 and
4.7). The floodplain could have exhibited high water table levels until the middle-Classic
(supported by a change in PCA1 values in Figure 4.5), since low values of Cyperaceae
indicates flooded environments (e.g. deep waters). Although Cyperaceae represents
azonal vegetation of aquatic environments, it has been found that its preferred
establishment conditions are from shallow waters at shore locations in lakes and
floodplains, but not deep waters (Van’t Veer and Hooghiemstra, 2000). The increase of
water table and periodic floodings in the floodplain could be the result of Mayan
hydraulic management that included the production of canals, water reservoirs, and raised
fields for agriculture (Beach, 2003). A rise in water table may have precluded the
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successful colonization of other aquatic plants that prefer shallower shore conditions such
as Polygoynum and members of the Apiaceae, Juncaceae and Typhaceae families (Berrio
et al., 2002). Another explanation for the decrease in Cyperaceae involves removal
related to anthropogenic use and management (Macia and Balslev, 2000). Ordinations
including NAP modern data show that similarly high percentages of Cyperaceae are
found both during the late-Classic and modern times, possibly because both time periods
are characterized by minimal minimum hydraulic or agricultural management, and
therefore flooding events (Figure 4.7). Archaeological work in the floodplain is needed
in order to be more conclusive about the existence of such agricultural structures.
Analysis of quantity and size of macroscopic and microscopic charcoal throughout the
core will complement hypotheses on the use of the site for Mayan agriculture.
Pinus values from the Preclassic are lower than at present, suggesting the presence of an
agricultural regime during the Preclassic period on the floodplain. Pinus is generally one
of the first trees to colonize open areas and is traditionally appreciated as a pioneer
species in vegetation succession (Conserva and Byrne, 2002). The fact that Pinus does
not ever seem to increase in abundance could be evidence that Pinus was under Mayan
management (i.e. fuelwood and ceremonial uses), which prevented its colonization in
agricultural fields and environs (e.g. valley slopes). During the Preclassic, Classic, and
Postclassic, the floodplain generally remains an agricultural center, characterized by
surrounding open landscapes with isolated shrubby patches of Myrica interspersed
throughout the environment. Some minor changes in arboreal content, however, may be
signalling small regional changes in landscape structure.
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Figure 4.7. Principal Component Analysis (PCA) of modern pollen rain samples from Purulhá highlands and sampled levels from core P-4. Triangles represent bryophyte polster modern samples, diamonds are modern surface sediments, and (+) are sedimentary records.
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Arboreal pollen values gradually increase through to the late-Preclassic (from 12 to 18%),
probably due to a decrease in agricultural activity associated with the Mayan Preclassic
collapse (Arnauld, 1987; Dahlin et al., 1987). According to modern pollen calibration
(Chapter 3), Poaceae pollen may be highly represented (i.e. less than 20%) in the
background signal from continuous forest because it is always found in low values.
Cyperaceae and Polygonum (notably successful in shallow water shore environments)
increase at the transition, likely as a result of lowering water-table levels on the
floodplain caused by temporary abandonment of strict water management practices (PCA
1 values slightly increase). It has been observed in Pacific Ocean coastal pollen records in
Guatemala that as mangroves decrease due to environmental changes (sea level drop
5500 yrs BP), aquatic plants such as Cyperaceae increase (Neff et al., 2006). In the
floodplain Asteraceae values decrease as the temporary and partial halt to large-scale
agriculture allows colonization from other herb species. Amaranthaceae-Chenopodiaceae
pollen increase at this time indicating onset of secondary succession on some but not all
plots as Zea pollen remains present at this time. From the onset of the Classic until the
end of the Postclassic period, arboreal pollen values once again decrease, likely due to a
reestablishment of large-scale agricultural practices in the floodplain.
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Figure 4.8. Cahabón River and its floodplain. Series of 3 arrows indicate river flow direction. N= North, masl=meters above sea level. Taken by J.C. Berrio © 2006.
4.4.3 Classic-Postclassic transition and its effects on floodplain management
Based on the apparent absence of Zea pollen in the P-4 core at the transition between the
Classic and Postclassic period, it is likely that large-scale agriculture is temporarily
locally abandoned (reflected as an abrupt change in PCA1 values). From the
anthropogenic point of view, absence of Zea pollen in Copán at the Classic-Postclassic
transition has been interpreted as a temporary abandonment of local agricultural land and
as temporary migration to nearby locations, and not necessarily a complete abandonment
(McNeil et al., 2010). However, this reconstruction has to be cautiously interpreted since
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the Classic-Postclassic transition samples have relatively low pollen concentration in P-4
core (Figure 4.1).
Recognizing that the Classical period in my study has few samples, careful interpretation
is needed when reconstructing the floodplain scenarios at this time. However, pollen
evidence indicates that possibly the start of the Classic (1780-1510 yrs BP) is
characterized by the stable abundance of agriculturally-related pollen (Zea). This possibly
determined the concomittant increase of Asteraceae that ecologically replaces (i.e.
successfully out-competes) Amaranthaceae /Chenopodiaceae. Towards the end of the
Classic (late-Classic to Terminal Classic, 1510-1240 yrs BP), Cyperaceae increases
markedly which suggests a possible abrupt drop in the water-table level of the floodplain
(i.e. because Cyperaceae is extremely successful in shallow water environments) due to
temporal abandonment of hydraulic management of agricultural terraces and raised fields.
This agricultural interruption is overlain by a background signal of decreasing arboreal
pollen. Geological and geomorphological analyses (e.g. particle size analysis) of the
floodplain will allow in the future a more complete reconstruction of the fluvial dynamics
at the headwaters of the Cahabón River.
An arid climate event associated with an increase in solar activity is identified around ca.
1200 yrs BP by Hodell (2007) using stable isotope and lithological evidence from Lake
Punta Laguna in the Yucatán Peninsula. Titanium evidence, used as a proxy for the
strength of the hydrological cycle, taken from the Cariaco Basin in Venezuela suggests
that this drying event was widespread as three centennial periods of reduced rainfall were
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reconstructed at that site for ~1190, 1140, and 1090 yrs BP (Haug et al., 2003). The P-4
core could be interpreted as indicating that agricultural practices were abandoned at the
floodplain possibly related to a drought related event. A decrease in LOI values from 12
to 9% at the Classic-Postclassic transition (60 cm depth) could suggest a slight decrease
in organic matter contribution to overall sedimentation. This decrease in LOI is supported
by increments in percentages of Cyperaceae and Poaceae (PCA1 values), as both expand
when water table lowers.
However, the occurrence of a drought is not likely for the Cahabón River Floodplain, as
this lowering in the water table could be due to cultural management (e.g. abandonment
of agricultural terraces) since the percentages of Cyperaceae and Poaceae at the Classic-
Postclassic transition are similar to present day when no drastic drought has been
registered (Figure 4.7). It is possible that agricultural practices were temporarily
transferred to a different location along the floodplain as a regular practice, as suggested
by pollen reconstructions by McNeil (2010) for Rio Amarillo in the Copán Valley
(Honduras). Analysis of stable oxygen isotopes is needed to permit more conclusive
inferences about drought occurrences in the Las Verapaces highlands.
Climate as a causal element for the Mayan collapse during the terminal Classic is still a
contentious issue (Aimers, 2007; Powell, 2008). Agriculture at the Cahabón floodplain
during the Classic-Postclassic transition may have been temporarily abandoned (i.e. as
Zea pollen absence suggests) but the reappearance of Zea pollen during the Postclassic
indicates that agriculture is likely re-established. The recovery of agricultural activities at
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the floodplain seems to contradict theories postulating a complete and widespread
collapse of Mayan societies across Mesoamerica (Arnauld, 1988; Borgstede and Mathieu,
2007). On the other hand, if the temporary disappearance of Zea represents a counting
artefact for P-4 core, continuous agricultural activity is supported during the Classic-
Postclassic transition. However, changes in other pollen taxa (e.g. Aquatics and
Asteraceae) during this transition support temporally local abandonment of the Cahabón
floodplain.
The hypothetical abandonment of the floodplain at this transitional period (Classic-
Postclassic) allowed a change in vegetation succession to take place, possibly due to a
halt in hydraulic management operations which led water levels to decrease abruptly. By
the time that agriculture is re-established at the Postclassic (indicated by the reappearance
of Zea pollen), Cyperaceae reaches the lowest values (from 138 to 29%) as an indication
of a higher water-table related to artificial flooding (e.g. deeper waters). The marked
decrease in sedimentation rate from 0.036 to 0.018 cm yr-1 during the Postclassic supports
the continuity of soil conservation practices in the Cahabón floodplain (Figure 4.1),
although possibly with less complex hydraulic management (i.e. less water volumes in
channels). A two-fold increase in LOI (9 to 16%) suggests secondary vegetation
succession taking place at the floodplain environs (i.e. increase of organic matter input),
as pollen from Asteraceae and Amaranthaceae/Chenopodiaceae increase temporarily at
this time. Cyperaceae is being replaced by trilete spores (increase from 42 to 107%) and
monolete spores (increase from 18 to 41%). Based on modern day calibration (Figure
3.5), the former may indicate for the Postclassic a temporary forest recovery (i.e.
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scattered forest remnants) because trilete spores may represent tree fern taxa found in
forested environments (e.g. tree ferns from Cyatheaceae family) (Van’t Veer and
Hooghiemstra, 2000), while the latter supports disturbance due to landscape management.
Archaeological evidence from the terminal Classic in the Maya highlands at Las
Verapaces indicates a vigorous creativity and imagination at the ceramics production
level (Arnauld, 1987), which possibly means that although activities at the urban centers
may have not halted nor declined, they may have temporarily at the agricultural centers,
such as the Cahabón floodplain.
4.4.4 European conquest and possible climatic variability
The end of the Postclassic is clearly characterized by a change in pollen assemblages in
the P-4 paleoecological record (over 270 yrs, during the period 420 to 150 yrs BP) (PCA1
values show a marked change). A critical increase in sedimentation rates (from 0.018 to
0.17 cm yr -1) may be indicating that soil conservation practices have been abandoned and
that agriculturally-related structures such as terraces have been removed. According to
historical documents from Catholic Dominic Missionaries (Godoy, 2006), approximately
eight cities (e.g. including Cobán and Purulhá) in the Las Verapaces region were located
along the Cahabón Floodplain, all established in a 30-year period from ca. AD 1544 to
1574. This 30-year period falls within the 400-year period characterized by the decrease
of Zea pollen as a result of the onset of the European Conquest (~400 yrs BP). Due to
decreasing water-table levels on the floodplain, Cyperaceae once again becomes a
dominant pollen type, trilete spores decrease possibly due to diminishing forest cover,
and monoletes spores maintained relativey high values due to high levels of disturbance.
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Asteraceae co-dominates with the disturbance related taxon Alternanthera (Marchant et
al., 2002), which appears for the first time along the core. Although not an exotic species
in Latin America (i.e. found in Amazonian pollen records dating to 8 ky BP), the
presence of Alternanthera is related to abrupt land-use change, abandonment of
traditional agricultural practices in the floodplain and the installment of different
European management regimes (i.e. Colonial period and modern times) (Behling et al.,
2001).
A critical change in land management at the time of the European conquest is supported
by other patterns observed in the P-4 core. Increases in Hedyosmum pollen may show
development (succession) of the lower montane and montane forest during the 16th
century, while Quercus pollen decreases temporarily (close to 1%). It is possible that
selective forest management is being practiced, because while Quercus is extracted for
timber and fuelwood (Ramírez-Marcial et al., 2001; Ramírez-Marcial, 2003),
Hedyosmum stands appears to have been left unaffected based on P-4 pollen record.
Pinus pollen increases several-fold during this time period and this could be explained by
the fact that Pinus is a pioneer in disturbed conditions (Richardson, 2000). Similarly,
based on pollen records, pioneering colonization by Pinus has been suggested during the
same period at Laguna Azteca in Central Mexico (Conserva and Byrne, 2002). On the
other hand, in a 4200-yr paleoecological study at Sierra Manantlan Biosphere Reserve in
the West-Central Mexican highlands, under low to null human disturbance, Pinus
colonization responded positively to intervals of aridity (Figueroa-Rangel et al., 2008).
During the 20th century until the present, Pinus pollen decreases (reflected in a change of
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PCA1 values) (Figure 4.1) probably due to extraction of pine trees for timber use, and
because of land use change in the floodplain to cattle pastures and agriculture, which are
now a more serious threat for forest species conservation than climate change (van
Zonneveld et al., 2009).
Indicator pollen type from higher elevation (mixed montane forest) Abies briefly appears
for the first time in the sedimentary record at the onset of the European conquest (422 yrs
BP), and remains present until the 20th century (Figure 4.1). Appearance of Abies in the
P-4 pollen record matches approximately solar minima events experienced at the time of
the Little Ice Age ca. 300-400 yrs BP (Helama et al., 2009). A Mesoamerican regional
drop in temperature, associated with drier conditions has been identified in sedimentary
records from the Yucatán lowlands (Hodell et al., 2005, 2007), and lakes Zempoala and
Quila in Central Mexican highlands (Almeida et al., 2005). On the other hand, in Lago
Verde, Los Tuxtlas in Mexico (Lozano-García et al., 2010) humid conditions 300-400 yrs
BP promoted an increase in abundance of pollen of upland vegetation. Core P-4 and other
highland pollen records may support differential effects of the Little Ice Age cooling
event, in general terms increasing aridity in the lowlands and increasing humidity in the
highlands. Temporary decreases of Abies and Myrica pollen (~300-100 yrs BP) are
possibly explained by increases in regional and local timber harvesting and land clearing
by Spanish colonizers, respectively (Islebe and Hooghiemstra, 1995; Andersen et al.,
2006). Land clearing at the Cahabón valley slopes, led possibly to Myrica’s niche
occupation by Pinus. Despite of the currently deforested landscape conditions (~60%
forest removal) at the Cahabón floodplain, there seems to be an increase at present in
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pollen indicative of the Montane Cloud Forest and Mixed Montane Forest vegetation
belts, possibly due to recent conservation efforts (CECON, 1999; Jolon-Morales, 2007).
4.5. Chapter Summary
Changes in fossil pollen spectra in the P-4 core from the Cahabón River Floodplain
corresponded to transitions between Mayan cultural periods and the start of the European
conquest (ca. 350 yrs BP). The geographical location of the headwaters of the Cahabón
River, where the P-4 core was collected, fulfills geomorphological conditions for the
possible existence of a paleolake in the plateau where currently the floodplain exists. LOI
values (ca. 10%) and the non-preservation of pollen support the paleolake explanation.
Agricultural practices are inferred from the appearance of pollen, which is mainly non-
arboreal (e.g. Asteraceae and Zea), together with slight increases in LOI values (>10%)
and low values of Cyperaceae pollen (which prefers shallow water in shore
environments). Based on this evidence it is believed that Mayan agriculture was
developed during the transition from lacustrine to floodplain conditions. Sedimentation
rates on the floodplain decreased many-fold ca. 360 yrs after the first pollen appearance,
which is possibly evidence for the development of agricultural terraces that eventually
dimished and controlled locally soil erosion.
During ca. 2000 yrs of agriculture there is evidence of a temporal abandonment of
agriculture in the floodplain during the Classic-Postclassic transition, because temporarily
Zea pollen disappears, Cyperaceae and Poaceae pollen increase (e.g. less flooding of
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terraces), and LOI slightly decreases (12 to 9%). Effects of the occurrence of the known
Mesoamerican megadroughts are not obvious in the floodplain record presented here,
since the temporary increase of indicators of dryer conditions (e.g. Cyperaceae and
Poaceae) have values similar to current ones according to modern pollen rain calibrations
when no droughts are registered. The appearance of Abies pollen in sedimentary record at
the end of the Postclassic ca. 350 yrs BP could be an evidence of regional cooling
conditions related to the Little Ice Age cold event.
Agriculture re-establishment during the Postclassic (e.g. Cyperaceae and Poaceae pollen
decrease, and Zea pollen reappears) is completely halted by the European conquest, as
evidence of disturbances is registered in the sedimentary record, including: abrupt
increase of sedimentation rates (0.018 to 0.17 vm yr-1), appearance of disturbance related
pollen taxa (e.g. Alternanthera), increase of Cyperaceae pollen due to change in land use
(e.g. lower water table for non-agricultural land use, such as cattle pastures), and increase
of Pinus pollen; Pinus colonizes areas that have been cleared for timber extraction and
the development of European colonies. The major change in the sedimentary record is
related to environmental disturbances after the European conquest over ca. 300 yrs, never
seen before in 2000 yrs of history.
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Chapter 5:
The Lachuá Lowlands Rain Forest in Guatemala: 2,000 yrs of forested landscape?
5.1 Introduction
Along the banks of the Chixoy River at the foothills of the Sierra Chama and south of the
Petén Lowlands, there was a city known as Salinas de los Nueve Cerros (Figure 1.2 and
1.3). It was located in a unique landscape, at the intersection between highlands and
lowlands, and was a city known to play an important role as salt producer since Preclassic
times. The city epicentre is located around the Tortugas and Nueve Cerros hills, where
salt extraction took place from an exposed salt dome (Andrews, 1983; Woodfill, 2012).
The city is located close to the floodplain of the Chixoy River, a likely location for
agricultural activity. Salinas de los Nueve Cerros probably reached its climax during the
late-Classic and was abandoned during the Postclassic; its abandonment was likely in
response to the reduced important of salt production during the Terminal Classic, when
major cities no longer required large quantities of salt (Arroyo, 1994). Perhaps due to its
reliance on salt as an economic resource, the surrounding forest was likely less disturbed
than cities that relied on large-scale agriculture. Scientific expedition reports dating to the
the 16th century, indicate that the area around Salinas de los Nueve Cerros was likely
covered in dense and continuous forest. By ca. 1950, the region still had a forest cover
close to 100%, although currently it has decreased to ~50% (Avendaño et al., 2007).
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Archaeological studies indicate that land use intensity (i.e. agriculture) increased towards
the epicentres of Mayan cities (Johnson et al., 2007), leaving outskirts with less urban
development, however in some locations urban and rural land use intensity was similar
(Beach et al., 2009). Agriculture was developed using a variety of strategies, such as
stone boxes, terraces, swidden techniques (i.e. slash and burn), including crop rotation
and forest management (e.g agroforestry) (Demarest, 2005). Agroforestry involved the
combination of agriculture and management (silviculture) of beneficial trees (e.g. food,
medicines, tools, construction, ceremonial), in a strategy that imitated forest structure and
distribution patterns, in the so-called Maya forest gardens (Ford and Nigh, 2009; Ross,
2011). Silviculture was probably more intense than agriculture in furthest points from city
epicentres as population density decreased.
The overall objective of this study is to examine a sediment record spanning 2000 years
from a wetland located next to Lake Lachuá, approximately 5 km southwest from Salinas
de los Nueve Cerros and within the Lake Lachuá National Park. This region is of interest
because it lies in a transition zone between the lowlands and highlands of Mayan
occupation and has not yet been studied. The Lake Lachuá National Park is currently the
last remnant of tropical rain forest in the Franja Transveral del Norte region. The past 60
years has seen much disturbance of natural forests due to (1) colonization of displaced
populations, (2) introduction of export cash crops, and (3) most recently oil exploration.
Since this region has a rich history of human-environment interactions spanning pre-
Hispanic to post-Colonial times, I expect that most changes to vegetation will have some
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relation to human land management and not to climate change. Calculations of the
approximate age of the existing remnants of tropical rain forest at Lake Lachuá National
Park should enrich discussions of forest conservation, in particular, the baselines
necessary for successful conservation of biological diversity.
5.2 Methods
5.2.1 Core Sampling and Laboratory Work
With the use of a Livingstone Corer, I extracted a ~0.5 m core from the Lachuá Lowlands
in a wetland located at the northeast section of the Lachuá Lake (labeled as L-3), at
approximately 10 m from the shore (Figure 1.3). The location of L-3 core was cautiously
selected in order to avoid any disturbance from modern hydrological modifications,
landslides or incoming or outflowing rivers. Coring was stopped once it became
impossible to continue due to stiffness of sediments.
The top centimeter of each core was separated for modern pollen rain calibration
(Chapter 3), and the rest was wrapped in aluminum foil and enclosed in a PVC pipe. A 1
ml sub-sample was taken every 2.5 cm along L-3 core. Sub-samples were stored in
Ziploc bags, and the core’s stratigraphy was qualitatively described. After proper
labeling, the core and the subsamples were stored in a cold room.
According to the Department of Geography Protocol (No. 010) of the University of
Leicester, samples were pre-treated overnight with pyrophosphate, followed by standard
acetolysis procedure and heavy liquid separation with the use of bromoform (Fægri and
137
Iversen, 1989). Exotic Lycopodium spore tablets were added as markers to calculate
pollen concentration. Pollen counting was completed to 200 grains per sample when
possible (Lytle and Wahl, 2005). Pollen sum included arboreal and non-arboreal taxa that
were identified to family and genus level. Unknowns, spores and aquatics (Cyperaceae)
were not included in the pollen sum (Fægri and Iversen, 1989) and their abundance was
measured as a ratio in relationship to the total pollen sum per sample.
Arboreal pollen (AP) and non-arboreal pollen (NAP) percentages were calculated to
represent local landscape vegetation cover. The Paleoecology Laboratory Loss of ignition
(LOI) protocol from the University of Toronto (Heiri et al., 2001) was applied for each
subsample where pollen was analyzed (see above), to calculate the organic (550°C),
inorganic (950°C), and silicate (% left) contribution to the sediment sample (estimated
2% error in the measurement). Only the LOI at 550°C is presented and referred as "LOI";
it is expressed as percent of dry mass In the L-3 core, a bulk sample from the lowest level
(47.5 cm in depth) and one additional sample (22.5 cm in depth) were radiocarbon dated
to develop models of sediment accumulation rates. Dates were calibrated through the use
of the IntCal04 curve from CALIB 6.0 (Stuiver et al., 2005).
5.2.2 Core data analysis
Pollen counts were tabulated for pollen types and core levels, including for the surficial
level, for comparison with the modern pollen rain data presented in Chapter 3. Arboreal
and non-arboreal pollen types were included in the pollen sum, excluding aquatics (e.g.
Cyperaceae), pteridophytes spores, and unknowns. For pollen concentration, all counts
138
were included. Principal component analysis (PCA) was performed with the statistical
package PAST (Hammer et al., 2001) to describe changes in pollen spectra along the core
including common and rare taxa. The software C2 (Juggins, 2003) was used to construct
a stratigraphic diagram (based on depth measured in cm and calibrated time scale) based
on relative abundance of arboreal (temperate trees and shrubs) and non-arboreal pollen
types, aquatics, pteridophytes spores, LOI (loss-on-igition), sedimentation rate, and PCA
axes scores. The stratigraphic diagram was divided into zones according to cultural
periods defined for Mesoamerica (i.e. see Introduction, section 1.6).
An analysis based on nine regional studies and my data (Mexico and Central America)
spanning the Preclassic to colonial times (Almeida et al., 2005; Carrillo-Bastos et al.,
2010a; Conserva and Byrne, 2002; Dull et al., 2010; Figueroa-Rangel et al., 2008; Islebe
and Hooghiemstra, 1997; McNeil et al., 2010; Wahl et al., 2006) was performed in order
to compare my calculated sedimentation rates with values found in other Mesoamerican
highland and lowland scenarios. The sites used in this regional comparison were placed
into groups according to elevation (0-500 m, 500-1000 m, 1000-2000 m, and 2000-3100
m) and cultural periods (Preclassic, Classic, Postclassic, and Colony), to determine if the
sedimentation rates in core L-3 were expected or outlier values for the groups to which
they belonged (see section 2.4.3 for further explanation). The analysis was
complemented with a Kruskal-Walis test to test the coherence of created elevation and
cultural period groups. The sedimentation rate values for core L-3 are compared to other
sites in the same elevational range (0-500 m), and across four cultural periods.
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5.3 Results
5.3.1 Stratigraphic description
The L-3 core is composed mostly of a homogeneous dark peat with some fine-grained
inorganic inclusions and scattered wood fragments, with no clear stratigraphic
differentiation. Wood fragments are identified along the core at different depths.
LOI values found at the bottom of the L-3 core are characteristic of wetland
environments (~ 80-90%), with variability in LOI observed along the core likely being
representative of human activity during known cultural periods of the Maya (Figure 5.1).
LOI between 47.5-45 cm core interval decreases gradually from 92 to 86%, during the
late-Preclassic period (i.e. core time interval 1835-1750 yrs BP). At the Preclassic-Classic
transition, LOI values decrease once again from 86-85% to 79% in approximately a span
of 90 years (time interval 1750-1580 yrs BP). LOI values remain relatively stable (75-
81%) for the remainder of the Classic period (1580- 1070 yrs BP). There is a notable
decrease in LOI values down to 68% shortly after the Classic-Postclassic transition (~90
yrs), but as it stands as a single point, it should be carefully interpreted. Decreasing LOI
indicates a relatively reduced contribution of organic matter into the sediment. During the
Postclassic and European Conquest-Colonization, LOI values remain stable around 82-
86%.
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Table 5.1. AMS radiocarbon dates, calibrates age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá. Bold numbers in brackets are the calibrated dates. All radiocarbon dates material is from bulk samples.
Depth (cm)
Lab. No
13C/12C
14C yrs BP
Age range 2σ and
Median Age (cal yrs BP)
22.5
Beta-281242
-27.8
990±40
795-(902)-964
47.5
GrA-40111 --- 1835±30 1705-(1773)-1864
5.3.2 Chronological control and sedimentation rates
The oldest age of 1835 yrs BP corresponds to sediments found at the bottom of the L-3
core at a depth of 47.5 cm (Table 5.1). The second date taken from the core is 990 yrs BP
and is found at a depth of 22.5 cm. The depth versus age model is very close to linear (r2=
0.99) although significance of this relationship will be tested when more radiocarbon
dates are obtained. Based on the L-3 chronological model, a relatively slow accumulation
rate of 0.026 cm yr-1 is observed, a value similar to the slow sedimentation rates observed
in the P-4 core (0.018 and 0.036 cm yr-1) during the time of Mayan agricultural
management of the Cahabón floodplain (see Chapter 4). The accumulation rate found for
the L-3 core (0.026 cm yr-1) is not an outlier in the groups they belonged according to
elevation and age (Figure 4.3). For further information about regional Mesoamerican
analysis of sedimentation rate values, see section 4.3.2.
141
0
5
10
15
20
25
30
35
40
45
Depth
(cm)
Guatemala
Postclassic
Classic
Preclassic
0
Asterac
eae
0
Poace
ae
0
Ama/Che
no
0
Zea
0 24 48 72
Monole
tes
0 16 32 48 64
Triletes
0
Cypera
ceae
0 20 40 60 80 100
LOI
0 50 100 150
Pollen
conc
entra
tion (
x100
0 grai
ns/cm
3)
-24 -12 0 12 24
PCA1
-12 -4 4 12 20
PCA2
200
400
600
800
1000
1200
1400
1600
1800
Cal yrs
BP
Herbs Pteridophytes
Figure 5.1. L-3 core paleoecological diagram taken from a wetland next to Lake Lachuá. AP = Arboreal pollen (%); LOI550 = Loss on ignition at 550°C; PCA1 and PCA2= Axis 1 and 2 scores from principal components analysis. Mayan cultural periods are shown. The Guatemala zone represents modern day Republic of Guatemala. Pollen concentration (x1000 grains/cm3).
Percent abundance
142
5.3.3 Description of pollen diagram
The variability found along the first and second axes of my principal component analysis
(PCA1 and PCA2) is consistent with the a priori pollen zones based on Mayan cultural
periods (Figure 5.2). Based on PCA1, primary variability is explained by a change in
vegetation composition from Solanaceae to Combretaceae/Melastomataceae, where
Solanaceae dominates from the late Preclassic until the Classic-Postclassic transition, and
then is replaced by Combretaceae/Melastomataceae (which in turn dominates until 100
years ago). There are other secondary changes in vegetation succession observed in
PCA1 that are explained below (see pollen zones). PCA2 is governed mostly by
variability in regional and local pollen rain, more specifically, by Ilex and a group of
tropical pollen types (e.g. Terminalia, Sapium), respectively.
I present in the pollen diagram common and rare taxa identified at least to genus and
family (Figure 5.3). Zones were closely related to four cultural periods: Terminal Pre-
Classic, Classic, Post-Classic, and Colonial to modern-day Guatemala. The two bottom
levels represent the Terminal Preclassic, where the Preclassic-Classic transition had no
pollen content. The non-arboreal pollen contribution is relatively low overall in the L-3
core (<10%).
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Figure 5.2. Principal Component Analysis (PCA) of sampled levels from core L-3. PCA1= scores along first principal component axis, PCA2= scores along second principal component axis. PC= preclassic levels, C=classic levels, PT=postclassic levels, G= Guatemala zone, Modern= represents surface sediment (0-1 cm).
144
Zone 1: Terminal Preclassic (1835-1750 yrs BP)
Information about vegetation from the Terminal Preclassic comes from the second last
level, since both the bottom and the Preclassic-Classic transition levels contain no
preserved pollen. Despite the fact that the bottom level at 1835 yrs BP has no preserved
pollen, the highest LOI value (92%) at L-3 core is observed at this level, and may be
related to a higher vegetation cover in the wetland (i.e. less opened-up landscape).
Possibly oxidation processes at both levels due to temporarily dessication (e.g. lower
water levels) resulted in null preservation of pollen.
Solanaceae dominates the pollen assemblage from this single sample dating to the
Preclassic (32%) to the late-Classic, with other taxa such as Alchornea and Spondias co-
dominating at ~5%. Other tropical taxa such as Psychotria, Combretaceae
/Melastomataceae, Bursera, Rubiaceae and Terminalia are present at lower values (1-
7%); while Arecaceae, Brosimum, Caesalpinaceae, Celtis, Malphigiaceae, Myrtaceae,
Pachira, Sapium, Sapotaceae, and Trema are absent when compared to modern samples.
At 1750 yrs BP (end of the Preclassic), the temperate taxon Myrica co-dominates with
Solanaceae at 26% and shows a positive correlation for the rest of the core. Regional taxa
Pinus and Quercus are present at intermediate values (6 and 4%, respectively), Alnus and
Hedyosmum at low values (1%), and Hyeronima and Abies are absent during this period.
In fact, Hyeronima, Abies and Alnus are regularly absent at locations along the core.
Although Ilex is at low values (2%) in this period, it will soon become an important taxon
for explaining variability along the core.
145
0
5
10
15
20
25
30
35
40
45
Depth
(cm)
Guatemala
Postclassic
Classic
Preclassic
0 20 40
Solana
ceae
0 20 40
Comb/M
elas
0 20
Myrtac
eae
0
Alchorn
ea
0
Rubiac
eae
0
Spond
ias
0
Termina
lia
0
Sapium
0 20
Psych
otria
0
Arecac
eae
0
Malphig
iacea
e
0
Bursera
0
Sapota
ceae
0
Piper
0
Celtis
0
Brosim
um
0
Trema
0
Bomba
cace
ae0
Caesa
lpina
ceae
0 20Ile
x0
Hedyo
smum
0
Hyero
nima
0 20
Myrica
0
Quercu
s
0 20
Pinus
0
Abies
0
Alnus
0 20 40 60 80 100
AP
-24 -12 0 12 24
PCA1
-12 -4 4 12 20
PCA2
200
400
600
800
1000
1200
1400
1600
1800
Cal yrs
BP
Tropical trees and shrubs Temperate trees and shrubs
Figure 5.3. Pollen percentage diagram of L-3 core from a wetland next to Lake Lachuá. + = taxa appearing at <1%. Mayan cultural periods are shown. The Guatemala zone represents modern day Republic of Guatemala.
Percent abundance
146
Non-arboreal pollen contribution is low (4%) and is characterized by Asteraceae and
Poaceae pollen. Cyperaceae is present at intermediate values (3%) and only increases
significantly at the end of the Classic and in modern times (8%). Monolete and trilete
spores show relatively intermediate values (34 and 23 %, respectively) during the late-
Preclassic.
Zone 2: Classic (1750-1070 yrs BP)
Although Solanaceae dominates during the Classic (32%), it shows a subtle decreasing
trend (down to 25%) up to the Terminal Classic (1070 yrs BP) when it is replaced by
Combretaceae/Melastomataceae. Combretaceae/Melastomataceae experiences a decrease
in abundance during the middle Classic (from 9 to 6%), but progressively increases
towards the Terminal Classic (18%). Some arboreal taxa decrease in abundance at the
Terminal Classic, behaving similarly to Solanaceae. These taxa include Alchornea (8-
5%), Psychotria (16-1%), and Rubiaceae (5-2%). Myrtaceae increases during the Classic
(15-4%) and abruptly decreases at the Classic-Postclassic transition or shortly thereafter.
The regional taxon Ilex (9-3%) follows a similar increasing and abruptly decreasing
trend.
Regional taxa, Myrica and Pinus, show a decreasing trend from the onset of the Classic
towards the Postclassic. Alnus appears during the early-Classic (1%) and slightly
increases at the Classic-Postclassic transition (~2%). Other arboreal taxa are scarcely
present, although Arecaceae, Bursera, Celtis, Malphigiaceae, Sapotaceae and Trema
appear in minor abundances during the Classic. Herb species (Asteraceae and Poaceae)
147
and Cyperaceae are also scarce until the Classic where they appear in minor abundance.
Zea appears only once in a very low abundance (1%) during the early-Classic, and
reappears (~2%) continuously until the modern period (110 yrs BP). Abundances of
monolete spores are relatively low, while trilete spores have their maximum relative
values during this period. Both show a sharp peak at the Classic-Postclassic transition (as
they did during the late-Preclassic).
Zone 3: Postclassic (1070-440 yrs BP)
Solanaceae (~22%) and Combretaceae/Melastomataceae (~23%) co-dominate during the
early Postclassic, and then the former progressively decreases until the present.
Combretaceae/Melastomataceae has a bell shaped dominance curve during the
Postclassic, reaching a maximum (33%) at the middle-Postclassic (770 yrs BP).
Following Combretaceae/Melastomataceae decreases until the late-Postclassic (22%),
remaining nevertheless as dominant taxon during cultural period. Other arboreal tropical
taxa such as Myrtaceae, Alchornea, Rubiaceae, and Spondias are present at low and
intermediate values (2-14%) without showing a stable pattern. Some arboreal taxa,
Terminalia, Sapium, Malpighiaceae and Psychotria, are consistently present in the core
but at lower values (1-4%). The remaining arboreal taxa, such as Arecaceae,
Bombacaceae, Bursera, Celtis, Sapotaceae and Trema, are present in few levels at low
values (~1-3%) as they are during the Classic period. Brosimum pollen is present at low
values (~1%) for the only time in the L-3 core.
148
Temperate taxa like Myrica, Quercus and Pinus are generally less abundant during the
Postclassic. In contrast, Ilex shows an abrupt increase during the early Postclassic
(represented by a change in PCA2 values), although overall it generally maintains
intermediate values throughout the core. Hyeronima reappears and increases during the
Postclassic (1-4%), whereas Alnus reappears and remains relatively stable (1-2%) during
the Postclassic. Herbs and Cyperaceae maintain a similar pattern from the Classic and are
not abundant (<4%). Monolete spores gradually increase during the Postclassic, while
trilete spores decrease markedly in abundance.
Zone 4: Colonial to Modern Guatemala (440 yrs BP-Present)
Solanaceae and Myrtaceae maintain intermediate values (7-12% and 4-13%, respectively)
in the last ca. 400 yrs. Combretaceae/Melastomataceae increases at the onset of the
Colonial period (from 22-32%) and then decreases towards the present (15-6%).
Alchornea, Rubiaceae, and Spondias show a decreasing tendency towards the present (ca.
7 to 1%), whereas Terminalia, Sapium and Psychotria show an increasing trend towards
the present (ca. 2 to 9%). Tropical arboreal taxa like Bursera, Sapotaceae, Celtis, and
Malpighiaceae are present at low values (<2%). Trema slightly increases its abundance
up to the present-day (1 to 2%).
Ilex, Pinus and Myrica progressively increase towards the present-day (~ 3 to 15%),
whereas Hyeronima stays stable until it disappears from the modern-day sediments. Alnus
is present only at low values (~1%) during the Colonial period and then disappears, and
Quercus slightly increases towards the present-day (1 to 3%). Asteraceae and Cyperaceae
149
maintain low values at 2-5% and 1-8%, respectively. Poaceae begins at a low value and
decreases at the present. Zea appears for the second time ca. 110 yrs BP. Monolete and
trilete spores disappear at 220 yrs BP and then monolete spores show an abundance peak
110 yrs BP and trilete spores present their lowest relative values.
5.4 Discussion
5.4.1 Role of cultural management and vegetation succession
Pollen information from our L-3 core is likely supporting the existence of Mayan forest
management practices close to Lachuá Lake at the outskirts of Salinas de los Nueve
Cerros (Figure 5.4). Pollen of arboreal taxa that have been identified as important tree
species to the Maya (e.g. Psychotria, Spondias, Terminalia) have been found in L-3 core,
in addition to high arboreal pollen percentages (as much as 80% or more abundance) that
reflect a densely-forested portion of the landscape. At the Classic-Postclassic transition,
vegetation succession likely reflected cultural activities. For example, dominance of
Solanaceae pollen in L-3 core from the Preclassic to the Classic indicates managed forest
because this pollen type is an indicator of shrubs and small trees taxa of secondary
succession (e.g. Cestrum, Lycianthes, Lycium) (Marchant et al., 2002). Some of these
taxa had economic use (e.g. Capsicum, Solanum). The eventual dominance of trilete
spores over monolete spores is possibly indicative of progressive successful forest
management since the former benefits from lower levels of disturbance, as modern pollen
calibration from Lake Lachuá National Park suggests that trilete spores are indicators of
closed canopy forest (Figure 3.4 and Figure 5.5). Monolete spores were found in lower
150
Figure 5.4. Location of the ancient Mayan city of Salinas de los Nueve Cerros on the banks of the Chixoy River, Alta Verapaz, Guatemala. Blue shaded area represents current known maximum spatial extension of Salinas de los Nueve Cerros (Woodfill 2011). Gray polygon represents Lachuá Lake National Park. Irregular black lines represent rivers. Inverse dark triangle represents L-3 core location next to Lachuá Lake (light gray polygon). Figure modified from Dillon (1977) and Woodfill (2011).
151
abundances in forest interior conditions according to modern pollen calibrations (Figure
3.4).
Salinas de los Nueve Cerros was a key salt producing center for many important Mayan
cities including the Petexbatún and Tikal kingdoms, and remained so until the end of the
Classic (Wright, 2005; Bachand, 2010). Decreasing Solanaceae pollen during the
Postclassic could be reflective of city abandonment (as reflected by a change of PCA1
values, Figure 5.1), where all major economic activities including cropping, selective
tree extraction and forestry ceased to occur due to a drop in the economic importance of
salt demand from larger cities facing major societal transformations (e.g. Tikal). The
process of abandonment at the Classic-Postclassic transition has been identified in
neighbouring Mayan cities of the Petexbatún Region, which is the location where it is
believed the Terminal Classic so called collapse started (Demarest, 2006).
Once forest management was possibly halted by the Classic-Postclassic transition,
vegetation succession was allowed to occur naturally, eventually resulting in dominance
of old-growth forest species such as Combretaceae/Melastomataceae (e.g. Combretum)
(Marchant et al., 2002) as seen in the L-3 core. Trends in pollen abundance within the
L-3 core support this hypothesis. Combretaceae/Melastomataceae pollen has also been
shown to increase at the onset of the Postclassic in other sites nearby, including Laguna
Naja (800 masl) located in the Mexican Lacandon Forest (Domínguez-Vázquez and
Islebe, 2008). The shift in Combretaceae/Melastomataceae dominance took
approximately 200 years after the onset of the Postclassic (PCA1 values notably reflect
152
change), wherein populations remained dominant for the next ca. 600 years, only
decreasing first 400 yrs BP and then abruptly during the last 150 yrs BP.
Information from our L-3 core strongly supports the possible existence of Maya forest
gardens located at the outskirts of the city-centre, Salinas de los Nueve Cerros. I found
pollen from taxa known to be planted by the Maya, including Terminalia, Spondias,
Psychotria, Myrtaceae, Rubiaceae, Sapotaceae, Arecaceae; and used by the Maya for
fuelwood, construction material, medicines, food (i.e. fruit, nuts), as well as latex
extraction (Ross and Rangel, 2011). The L-3 core contains these taxa in high abundance
during the Classic period, the heyday of Maya civilization (Schele and Freidel, 1990;
Freidel et al., 1993). Mayan gardens were planted so that the overall structure mimicked
the horizontal and vertical dimensions of a natural forest (Ford and Nigh, 2009). When
agroforestry likely ceased during the Classic-Postclassic transition, changes are recorded
in the L-3 core among the preferred Mayan garden tree species; some of them declined
abruptly and others disappeared for a short period. Nevertheless most of forest garden
taxa observed in the L-3 core persisted through Postclassic and Colonial times. The
occurrence of a detectable vegetation structure reflecting the composition of Mayan
forest gardens has been found elsewhere in ancient Mesoamerican sites (Ford, 2008;
Ross, 2011).
Forestry management may have been successful in reducing soil erosion, as stable LOI
values in the L-3 core suggest a continuous forest cover close to the wetland. Other
lowland and highland Mesoamerican locations have generally had similar sedimentation
153
rates as was found for L-3 core (Islebe and Hooghiemstra, 1997; Figueroa-Rangel et al.,
2008; Carrillo-Bastos et al., 2010), which is relatively slow (0.026 cm yr-1) and consistent
with forested conditions surrounding the wetland that prevent high inputs of eroded
materials into the peat. In tropical regions, LOI values above 75% (and even as low as
20%) have been traditionally described as containing wetland-marsh environments
(Berrio et al., 2002; Torres et al., 2005).
During the early-Postclassic when silvicultural practices were probably abandoned in
Salinas de los Nueve Cerros, LOI abruptly decreased from 78 to 68% indicate decreasing
organic matter contribution into the sediment load. Diminishing LOI values are probably
explained by decreasing organic matter contribution (i.e. increase of clastic material to
sediment load) (Shuman, 2003), due to deforestation as a consequence of temporary
forest gap openings. Similar patterns have been found in ancient peatlands in Georgia
near the Black Sea, where aeolian input increases in the sediment load due to more open
landscape conditions (de Klerk et al., 2009). The LOI decrease at this single level
(Classic-Postclassic transition) in L-3 core has been reported in a core from Laguna
Tamarindito in the Petexbatún region, with a drop from ca. 85 to 60% (Dunning et al.,
1998). Around the time of the city abandonment, changes in pollen abundances (from
disappearance to reduced values) of forest garden species in Core L-3 indicate a probable
abrupt increase in the extraction of valuable plant taxa (i.e. during socially unstable
transitional times). Monolete spores abruptly increase possibly reflecting temporary
invasion of forest gaps. Shortly after (~ 100 years later), LOI increases to values above
80%, indicating forest recovery wherein late-successional tree taxa such as
154
Combretaceae/Melastomataceae begin to dominate the pollen record. In the literature
regarding the neotropics, the problem of separating Melastomataceae (e.g. Clidemia for
lowlands and Miconia for highlands) (see Tables 2.1 and 2.3) from Combretaceae (e.g.
Combretum) pollen taxa has been discussed (Marchant et al., 2002), but it is believed that
possibly the former could be in higher abundances during early forest succession and
progressively replaced by the latter as succession develops (Pascarella et al., 2007).
Nevertheless, the Combretaceae/Melastomataceae pollen type has been found to be
representative of mature forests and seasonally inundated forest in Belize (Bhattacharya
et al., 2011) and South America (Gosling et al., 2009), such as the forest that surrounded
the wetland where Core L-3 was collected up until ca. 100 yrs BP when disturbances
related to salt extraction increased (Figure 5.3) (Dillon, 1979).
5.4.2 Baseline for forest conservation at Lachuá lowlands region
Co-dominance of pollen from Combretaceae/Melastomataceae and Solanaceae lasted for
approximately 200 yrs after the Classic-Postclassic transition (PCA1 values remain
relatively constant), likely indicating that some economic activities such as silviculture
and salt production remained, but soon began to decrease gradually up to the complete
abandonment of Salinas de los Nueve Cerros. Salinas de los Nueve Cerros is believed to
have been inhabited by scattered populations after its abandonment because its name
appears in colonial historical documents dating from 1625 AD (Godoy, 2006). It is
registered in such documents that salt extraction by Europeans started around 1626 AD,
which matches the decrease in Combretaceae/Melastomataceae (Figure 5.3, ca. 500 yrs
BP) probably due to related natural resources extraction in the nearby area (e.g. timber).
155
Salinas de los Nueve Cerros was identified as a critical location for salt production, an
economy that the Conquistadors felt they needed control to “pacify” local inhabitants.
Salt extraction was suspended for ca. 100 yrs due to local revolts, and resumed in the
early 1700’s until the 20th century (Dillon, 1979; Woodfill, 2012).
Despite continued activity at the Salinas salt mine, the surrounding vegetation shows
signs of recovery (ca. 300 yrs BP) because the pollen record is dominated by
Combretaceae/Melastomataceae. Similar pollen taxa were found to increase in abundance
during the Postclassic in the nearby tropical rain forest region of the Mexican Lacandon
Forest (e.g. Combretaceae /Melastomataceae and Myrtaceae) (Domínguez-Vázquez and
Islebe, 2008) and in the less humid Mirador Basin in Northern Petén (i.e. Combretaceae
/Melastomataceae) (Wahl et al., 2006). Forest in Lachuá environs likely remained
without intense anthropogenic management for approximately 800 yrs after its
abandonment during the Postlassic (PCA1 values remain relatively stable until ca. 150
yrs BP, Figure 5.1). Nevertheless, relatively low values of trilete spores and higher
values of monolete spores (McNeil et al., 2010), suggest some degree of disturbance.
Arboreal pollen from Combretaceae/Melastomataceae, Myrtaceae, Alchornea, Rubiaceae,
and Spondias that can tolerate low disturbance regimes begin to show decreases in
abundance during the last 150 yrs BP. On the contrary, Solanaceae benefit from
intermediate disturbance regimes as L-3 pollen pollen record indicates an increase, more
similar to what is found in modern times in bryophyte polsters (Figure 5.5). The present
day pattern of Solanaceae and Combretaceae/Melastomataceae pollen (Figure 3.3) could
156
be associated with the fact that the Lachuá Lake National Park was recently established
(1974 AD) (Monzón, 1999), so most likely the forest is still recovering from recent
disturbances occurring during the 20th century. Forest structure that prevailed from 770-
100 years BP changed dramatically during the 20th century, due to economic activities
that involved natural resources extraction, including salt production, oil prospecting
during the 1970’s, 1980's and 2000's, and arrival of displaced populations since the
1950's (Avendaño et al., 2007).
The remnant of tropical rain forest protected currently at Lake Lachuá National Park
(14,500 ha area) since the mid 1970’s is possibly more similar to the one that prevailed
during Classic times when forest gardens dominated land use at the outskirts of Salinas
de los Nueve Cerros (Figure 5.1 and 5.3). Present day PCA1 values are similar to PCA1
values during the Late Classic, suggesting similar disturbance levels.
A baseline to return to a “healthier” forest status (e.g. restoration) before recent
disturbances in the Lachuá environs could be considered to be the forest condition that
prevailed for approximately 800 years after Salinas de los Nueve Cerros was abandoned.
However, the core L-3 time span does not provide any reference for whether this 800-
year condition has an analog at earlier times before the Preclassic colonization at Lachuá.
The previous forest condition composed mostly of forest gardens lasted approximately
600-700 years was maintained under silvicultural principles which required deep
knowledge to imitate forest structure (Gomez-Pompa, 1991; Pyburn, 1998; Fedick,
2010). Although current arboreal composition is similar to the one from the Classic
157
-32 -16
PCA1
-20
-10
10
20
PC
A2
Figure 5.5. Principal Component Analysis (PCA) of modern pollen rain samples from Lachuá lowlands and sampled levels from core L-3. (+) represent bryophyte polsters modern samples, triangles are modern surface sediments, and inversed filled triangles are sedimentary records.
158
period, silvicultural practices are at the moment not being used and therefore current
forest management and disturbances may be leading forest into a new equilibrium state
with no previous analog (Whitehouse, 2010).
5.4.3 Lachuá Lowlands in the context of Mesoamerican Holocene paleoecology
The location of the L-3 core at the intersection between lowlands and highlands is
important in order to cross-correlate Mesoamerican regional paleoecology (Islebe and
Leyden, 2006) (Figure 3.1). The Lachuá lowlands are located in a wet (high
precipitation) zone that extends from Izabal at the Guatemalan Caribbean coastline to the
Uxpanapa region in the Gulf of Mexico; this contrasts with the much lower rates of
precipitation in the Yucatán Peninsula and the Petén lowlands (Imbach et al., 2010). The
high precipitation in this zone is believed to have been consistent in the long term
(Wendt, 1989), because it is hypothesized that partly due to resultant wetter conditions,
relicts (refugia) of tropical rain forest species were held during the last glacial cycle of
the Pleistocene.
For Mesoamerican sites located outside the zone of high precipitation, a series of
droughts occuring throughout the late Holocene (i.e. related to either insolation
variability or migration of the Intertropical Convergence Zone) have been found to match
important transitional cultural periods in Mesoamerica (i.e. Mayan Terminal Classic, the
Toltecs, the Aztecs and Spanish Conquest). These periods of drought have also been
correlated with extensive measurements from Cariaco Basin in Venezuela that also show
periods of low rainfall. Late-Holocene sites that indicate signs of drought in the paleo-
159
record are located in Central Mexico (Stahle et al., 2011), Northern and Southern
Yucatán Peninsula (Hodell et al., 2001; Carrillo-Bastos et al., 2010), and the Petén region
in Guatemala (Islebe and Leyden, 2006; Gill et al., 2007). Changes in vegetation inferred
from our L-3 sediment core do not support continued periods of droughts, because at
levels in the L-3 core where droughts are expected to be observed, there are no changes
in abundance of NAP pollen that could benefit from dryer conditions, such as Asteraceae,
Poaceae, and Amaranthaceae /Chenopodiaceae (Leyden et al., 1998; Wahl et al., 2006;
Wahl et al., 2007). Nevertheless, more high resolution exploration is needed in future
studies in the Lachua region, since temporal resolution of the L-3 core may not be
adequate to detect decade-long droughts that have been reconstructed for some sites in
the Mesoamerican lowlands.
The time of major variability within the pollen composition from L-3 core is at the
Classic-Postclassic transition (PCA1 values cross the zero threshold which indicates
opposing trends) and indicates culturally-driven dynamics and not natural climate forcing
(Figure 5.1 and 5.3). The changes in vegetation composition reflected in the L-3 core are
likely directly related to cultural management of Mayan forest gardens. Non-arboreal taxa
that tend to indicate occurrence of droughts (i.e. Asteraceae or Poaceae) do not show
consistent increases at the time of cultural transitional periods (Wahl et al., 2006). Pollen
and LOI information from the L-3 core both support a paleoclimate hypothesis of no
extended periods of drought, an observation that may be explained by the site's location
in the Izabal to Uxpanapa "wet belt". Other locations in this wet belt in Mexico have
shown evidence of humid conditions during expected dry conditions, such as the
160
Terminal Classic droughts in Laguna Atezca (Conserva and Byrne, 2002), and during the
Little Ice Age in Los Tuxtlas (Lozano-García et al., 2007). The use of other proxies, such
as oxygen isotopes, is needed in order to develop more conclusive inferences about the
occurrence of droughts in the Lachuá lowlands and nearby Petexbatún region.
There is considerable controversy surrounding the hypothesis that heavy deforestation by
the Mayans directly led to drying microclimate and ultimately the demise of Mayan
civilization. In contrast, evidence is surfacing from Copán in Honduras that indicates that
the low disturbance effects of the Mayan environmental management regime (Beach et
al., 2006) did not always lead to deforestation effects sufficient to have catalyzed the
Mayan Collapse (Fedick, 2010; McNeil et al., 2010). LOI values from core L-3 indicate
that possibly the management of Mayan forest gardens did not have a negative impact on
the environment, since wetland conditions were maintained in the region over centuries.
Nonetheless, further sedimentological analysis is needed to support our interpretations.
Forest management at Salinas de los Nueve Cerros did not result in a deforested
landscape, not even during its phase of maximal development during the Terminal
Classic. This is in stark contrast for Petén cities like Tikal where evidence for
deforestation is prevalent (Lentz and Hockaday, 2009) and supported by pollen data and
other proxies from different authors (Islebe and Leyden, 2006). To further support the
"no deforestation" hypothesis, sediment cores should be taken from the Salinas de los
Nueve Cerros city epicentre and nearby locations to differentiate between urban versus
rural land use change and correlating environmental impacts. More site-specific
approaches like the one applied in this study are likely more appropriate to
161
paleoecological-archaeological research because geographical heterogeneity is generally
considered more relevant in explaining cultural and environmental idiosyncrasies
(Aimers, 2007; Emery and Thornton, 2008; Beach et al., 2009; Demarest, 2009) than
assuming homogeneous responses across large expanses of landscapes and regions
(Powell, 2008).
5.5 Chapter summary
The fossil pollen spectra from the L-3 core indicate three major phases along ca. 2000 yrs
in the environs of the Lachuá Lake at the outskirts of Salinas de los Nueve Cerros. The
first phase spans over ca. 700 years of development of Mayan forest gardens (i.e. forestry
practices) mainly during the Classic, to its eventual abandonment at the Classic-
Postclassic transition ca. 1100 yrs BP. Main pollen taxa related to forest management and
economic uses are Solanaceae (related possibly to medium disturbance levels), and
Bursera, Myrtaceae, Sapium, Spondias, and Terminalia, respectively. The effects of
registered regional droughts at the Classic-Postclassic transition are discarded because
pollen taxa associated to dryer conditions (e.g. Poaceae and Cyperaceae) show no
significant increases relative to what is registered in the modern pollen rain.
The second phase is related to an increase in percentages of Combretaceae
/Melastomataceae pollen at the onset of the Postclassic, and to its eventual dominance in
the fossil pollen spectra during the next ca.700 years. Combretaceae/Melastomataceae
pollen in the L-3 core sedimentary record is associated with the prevailing forest
conditions after Salinas de los Nueve Cerros was abandoned due to a cease in major salt
162
production at the end of the Classic. The Mayan forest garden pollen “signal” is
maintained during the remains of this second phase until recent times (ca. 150 yrs BP) as
modern pollen rain calibration from L-3 core suggests. A minor drop in
Combretaceae/Melastomataceae pollen abundance ca. 500 yrs BP may be indicative of
the reactivation of salt production by European settlers, which may have disturbed the
forests at some degree since Solanaceae pollen abundance remains relatively constant
since then (ca. 10%). An increase in monolete and a decrease in trilete spores support the
changes observed in Combretaceae/Melastomataceae and Solanaceae pollen.
The recent phase dates back ca. 150 yrs when a decrease in Combretaceae
/Melastomataceae pollen percentages suggests an increase in the salt production by
European colonists in the region, and probably the extraction of other natural resources
(e.g. timber). In general terms, disturbance levels observed during the last 150 yrs in the
region are similar to the one observed during the Classic period according to PCA (which
reflect changes in abundance and composition of pollen spectra). The main difference
between recent times (150 yrs BP) and the Classic period, is that in the latter forest
management was well planned under complex forestry principles.
163
Chapter 6:
Conclusions
164
6.1 What are the factors that explain vegetation distribution along the
Las Verapaces environmental gradient and what taxa can be used as
"indicator species"?
Indicator plant taxa which had discrete distribution allowed me to delineate three
vegetation belts, which represent changes in vegetation communities along the Las
Verapaces elevational gradient in the Central Guatemalan Highlands and Lowlands:
Lowland Rain Forest, Lower Montane Rain Forest, and Montane Cloud Forest.
Generalist taxa smoothed the delineation of vegetation belts because of their continuous
distribution, and montane taxa that were distributed in lowlands informed me of the
existence of montane-like habitats beyond their expected elevation range (disjunctive
taxa).
The collation of unpublished vegetation inventories was effective as it was possible to
identify explanatory factors, such as elevation which in combination with temperature
variability (based on a temperature database) are the main criteria for vegetation belt
delineation. Other factors such as landscape position in topographically-controlled
drainage divides, and biogeographic origin provided complementary explanations.
Landscape position within a watershed and topographic variability (i.e. geomorphology
and underlying bedrock controls) influence vegetation distribution through their
relationship with dispersal processes and localized microclimate (physical and
physiological barriers). Patterns in the distributions of plant taxa along the Las Verapaces
gradient possibly reflect in part the biogeographic origin of taxa. Plant biogeography
165
integrates vegetation responses (i.e. physiological tolerances) to variability in elevation
and climate, with local relief determining whether or not an area is acting as a dispersal
corridor or barrier.
Iti is hoped that the research approach used in this study of the Las Verapaces gradient
serves as a model for future research in other parts of Guatemala as well as neighboring
regions in Mesoamerica. With future climate change and enhanced anthropogenic
disturbance of natural landscapes, there is a growing need for baselines from which to
compare future changes in vegetation communities. The present study contributes to this
objective. Moreover, the categorization of indicator, generalist and idiosyncratic taxa
permit more efficient and rigorous analysis of other meta-data bases, enabling better
decisions about conservation priorities and design.
166
6.2 Can paleoecological calibrations for fossil pollen be constructed
from a comparison of modern pollen rain from surface sediments and
bryophyte polsters?
In tropical regions, pollen spectra found in pollen reservoirs depend mainly on the
geographical location (i.e. lowlands or highlands) as it determines vegetation type and
related pollen production and dispersal mechanisms. Biogeographic origin of plants from
the highlands is mainly temperate or Laurasian, and therefore the major pollen dispersal
mechanism is anemophily; lowland plants have mainly zoophilous pollen dispersal
syndromes, because their origin is tropical or Amazonian. In spite of the fact that
anemophilous pollen can reach longer distances, analysis of bryophyte polsters from the
lowlands shows that zoophilous and local pollen taxa have in general a higher input than
in surface sediments, where zoophilous and anemophilous inputs are generally more
even. Pollen input in surface sediments and bryophyte polsters from highlands is
dominantly local and anemophilous, while input from lowlands due to wind transporation
is minimal. In general, some pollen taxa present in bryophyte polsters are “silent” in
surface sediments, because the former contains more pollen types from forest interiors
(i.e gravity and trunk space components, Faegri and Iversen, 1989).
Pollen spectra from small basins could have a higher local pollen input (especially if
surrounded by a high dense canopy vegetation) than mid to large sized basins (less barrier
effect from surrounding vegetation). Based on the collected information, it is believed
that if surface sediments are collected in a landscape that is forested to a large degree,
167
their pollen assemblages would be comparable to those found in bryophyte polsters from
forest interiors (i.e. high arboreal pollen content).
A preliminary modern pollen rain calibration has been developed in this study between
vegetation and bryophyte polsters and surface sediments, as a means to understand better
the pollen signal from the latter as it represents the best analogue for fossil pollen spectra
found in sedimentary records. The present calibration study is important because it covers
an unexplored important region in Guatemala; these data can be linked to the northern
Petén lowlands, and the Las Verapaces lowland and highlands, with the rest of
Guatemala and Mesoamerica in terms of palynological and paleoecological analyses.
168
6.3 What are the major vegetation changes recorded in the highland
core from the Las Verapaces region?
Paleoecological methods based on pollen and loss-on-ignition, aided in the reconstruction
of the paleoenvironmental history of the Cahabón river floodplain for the past ~2400
years. At the oldest date reported for the P-4 core (2390 yrs BP), possible ancient
lacustrine-like conditions are reconstructed for the floodplain, specifically a shoreline
environment where due to high rates of decomposition and oxidation, pollen absence is
explained. Initial agricultural exploration by Mayan populations at these earlier times
during the Preclassic could explain the higher sedimentation rate (0.25 cm yr-1) which
decreases (0.017 cm yr-1) once land management techniques minimized soil erosion. The
P-4 pollen record indicates agricultural activities (e.g. Zea and Asteraceae presence) at
the Cahabón river floodplain almost uninterruptedly for ca. 1700 yrs. One possible
explanation is that agriculture is interrupted first, temporarily at the Classic-Postclassic
transition (e.g. Terminal Classic) without having a significant impact on the culturally-
established floodplain dynamics; and later, completely at the European conquest and
colonization (e.g. Asteraceae pollen decrease), which marked a dramatic change in the
local vegetation dynamics (e.g. Pinus colonization) and floodplain sedimentation regime
(increase from 0.017 to 0.17 cm-1).
Nevertheless, in this mainly culturally driven sequence of vegetation changes, the
appearance of Abies, a higher elevation pollen taxon at the time of the “Little Ice Age”
(300-400 yrs BP), indicates the possibility of some vegetation change in response to
169
decreased solar activity, as seen in other locations in Mesoamerica (Lozano-García et al.,
2010). The linkage between lowering of water table and climatic forcing, such as the
occurrence of a drought at the Classic-Postclassic transition is temporarily discarded,
because Cyperaceae and Poaceae percentages increase to similar values observed in
present day when no major droughts are registered. Most likely temporary abandonment
of floodplain terraces for agriculture explains a possibly lower water table, since
maintenance is responsible of resultant water level rising. Recorded droughts in
Mesoamerica in particular for the Terminal Classic are not regionally synchronous, since
there are locations with no clear evidence of droughts such as in the Las Verapaces
highlands. However, more exploration is needed in this region to have a more conclusive
explanation about the existence of an agricultural centre in the Cahabón River floodplain.
Paleoecological exploration of highland environments in Mesoamerica is expanding, the
relevance of connections between lowland and highland Maya chiefdoms in cultural
evolution are better understood. In the face of non-existent lacustrine environments in
Las Verapaces highlands, such as it is in many geographical locations globally,
paleoecological analysis of riverine sediments in this study strengthens the use of
alternative reservoirs of paleorecords as a means to reconstruct natural and cultural
evolution of past landscapes.
170
6.4 What are the major vegetation changes recorded in the lowland core
from the Las Verapaces region?
The examination of a ca. 2000-year paleorecord indicates that vegetation changes in the
Lachuá region could be closely related to the history of the Mayan city of Salinas de los
Nueve Cerros. The L-3 core location holds the history of land management that took
place at the city's outskirts, where high abundance of pollen belonging to beneficial trees
taxa (e.g. Myrtaceae and Spondias) indicates that forest gardens could have been the
dominant land use. Cultural management of forest gardens determined vegetation
succession during the Preclassic and Classic cultural periods; these systems remained
mainly in a secondary succession stage, as indicated by the dominance of Solanaceae
pollen. At the Terminal Classic when the abandonment of Salinas de los Nueve Cerros
started, later succesional vegetation stages take place as inferred from
Combretaceae/Melastomatacae pollen co-dominance to an eventual complete dominance
for ca. 800 years after abandonment. It is not until ca. 150 yrs BP that vegetation changes
once again probably in the face of a different disturbance regime that involves major
natural resource extraction. In this case, Solanaceae pollen increases and pollen of
Combretaceae/Melastomataceae decreases.
Landscape evolution in the Lachuá lowlands over the development of Salinas de los
Nueve Cerros, including the Guatemalan colonial period, is determined mainly by
cultural factors. At the resolution level applied for the L-3 core, there is no clear evidence
of local occurrence of droughts reported elsewhere in Mesoamerica, especially at the
171
Classic-Postclassic transition. Changes in vegetation are believed to be more a response
to the abandonment of cultural management practices (i.e. forestry) and not to occurrence
of droughts since pollen benefited by drier conditions showed no change in their
abundances (e.g. Poaceae). Nevertheless, more high resolution paleoecological analysis
with more proxies (e.g. oxygen isotopes) is needed in future studies in the Lachuá region
to test hypotheses related to decade-long droughts in Mesoamerica.
It is critical to recognize vegetation succession in the long term, and not only analysis
based on forest cover percentage calculations because it may lead to unrealistic
interpretations in conservation biology (e.g. AP values). Despite the fact that arboreal
pollen percentages indicate that at the physiognomic level, Lachuá lowlands landscape
forest cover remains at values above 80% for ca. 2000 yrs, vegetation succession
indicates dynamics related to different management and disturbance regimes. The
question related to “What is natural?” is important to answer in order to understand
landscape natural and cultural variability and to incorporate it into conservation
management practices aided by paleoecological analysis.
172
6.5 What is the role of natural variability and cultural factors related to
the Maya Civilization in the evolution of landscapes in the Las Verapaces
Region?
Las Verapaces Region is located at an important transitional region between the Northern
Lowlands and the North Central Highlands in Guatemala. The pollen record of the last
ca. 2000 yrs BP has not shown any evidence of vegetation dynamics (i.e. succession)
driven by climate variability, especially at the time of the hypothesized droughts at the
Terminal Classic or Early Postclassic. Reduction in precipitation at that time period has
been hypothesized as caused by alterations in the latitudinal migration of the Intertropical
Convergence Zone (ITCZ), or ultimately by an increased aridity effect as a consequence
of intense land clearing, agricultural activities and high rates of deforestation,
respectively. Contrary to the latter hypothesis, Las Verapaces landscapes have an
important multi-centennial cultural imprint of successful Mayan management. Pollen
records indicate in on one hand the existence of agriculture at the Cahabón River
Floodplain, with possible soil conservation practices that led to the successful
establishment of an agricultural center (i.e. low sedimentation rates); and on the other
hand, a Mayan forest garden at the outskirts of Salinas de los Nueve Cerros in the Lachuá
region. In these scenarios, cultural factors possibly played an important role in the
evolution of landscapes, coupled with the influence of relatively climatic stable
conditions. Regarding natural factors, the lowlands to highlands gradient in the Las
Verapaces is located in a high precipitation and humidity envelop (i.e. known as the
173
Uxpanapa wet belt), a fact that contributes to its climatological stability, and thus in part
to its enormous biological diversity.
However, more exploration is needed in the Las Verapaces Region, in terms of collecting
longer Holocene records to examine landscape evolution at a longer temporal scale.
Inclusion of locations inside and outside of the “Uxpanapa wet belt” in future studies in
the Mesoamerican region will provide basis to explain thoroughly landscape evolution.
Inclusion of more paleoecological proxies (e.g. oxygen isotopes and macro and
microscopic charcoal) in future studies will enhance the understanding and the possibility
of testing hypotheses related to landscape evolution in terms of natural and cultural
factors.
Pollen records, LOI measurements, and sedimentation rates examined in this thesis
provided key information to support the idea that sustainable anthropogenic management,
if well planned, could enhance natural resources conservation. Lessons learned from the
paleoecology of the lowlands and highlands in the Las Verapaces include understanding
the negative effects that the European conquest and colony had on landscape dynamics
through drastic natural resource extraction. Even in the face of climatic and
environmental stable conditions, non-planned, non-measured and non-sustainable natural
resources management represents a threat to the conservation of biological diversity and
cultural legacies.
174
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Appendices
197
Appendix 2.1. Indicator, generalist, and disjunctive plant checklist.
Plant Taxa Axis 1 2466 2300 2200 2200 2100 2100 2000 1900 1900 1800 1800 1650 1500 1400 1258 1106 1048 1000 1000 600 400 200 170
Spondias mombin 109Tabebuia sp. 176Genipa sp. 226Inga sp. 257Saurauia belisensis 264Heliocarpus mexicanus 265Cedrela pacayana 266Perymenium grande 268Weinmannia pinnata 363Miconia aeruginosa 365Oreopanax liebmanii 373Psychotria parasitica 390Centropogon cordifolius 436Cavendishia guatemalensis 437Jocotillo 440Fuchsia microphylla 445Miconia glaberrima 445Styrax argenteus 452Lobelia nubicola 466Synardisia venosa 479Clethra suaveolens 498Phoradendron sp. 500Erigeron karvinskianus 526Passiflora sexflora 527Begonia oaxacana 555Ocotea sp. 557Rhynchosia sp. 655
Indi
cato
r T
axa
198
Appendix 2.1. continued. Idiosyncratic refers to Disjunctive Taxa.
Che4 Che3 Tin6 Pur5 Che2 Pur4 Pur3 Pur2 Che1 Pur1 Tin5 Tac Scruz Tin4 Che Flo Tam Bvta Tin3 Tin2 Chin Tin1 LachAxis 1 2466 2300 2200 2200 2100 2100 2000 1900 1900 1800 1800 1650 1500 1400 1258 1106 1048 1000 1000 600 400 200 170
Vochysia guatemalensis 153Terminalia amazonia 168Bursera simarouba 172Ceiba pentandra 190Parathesis vulgata 199Cecropia peltata 244Virola sp. 245Dendropanax leptopodus 269Mollineda guatemalensis 308Billia hippocastanum 312Engelhardtia guatemalensis 317Brunellia mexicana 330Persea donnell-smithii 333Liquidambar styraciflua 337Clusia sp. 368Hedyosmum mexicanum 384Quercus sp. 395Quercus crispifolia 442Myrica cerifera 512Eupatorium semialatum 549
Dendropanax arboreus 135Lasciacis divaricata 156Ocotea eucuneata 277Phoebe sp. 293Matayba oppositifolia 315Peperomia cobana 336Pouteria campechiana 338Clidemia capitellata 430Conyza bonariensis 499
Gen
eral
ist T
axa
Idio
sync
ratic
Tax
a
199
Appendix 3.1. Pollen types found on modern pollen calibrations and fossil pollen spectra from cores P-4 and L-3. Associated plant taxa and uses by ancient Mayan populations are shown. Information about vegetation belt (VB) is provided based on Table 2.2 and 2.3 (Chapter 2). * indicate know usage by modern Mayan populations.
Pollen taxa VB Genus
Family Associated plant taxon/taxa
Uses
Acacia Fabaceae Acacia spp. Medicine, forage, construction Alchornea Euphorbiaceae Anthurium Araceae
Araliaceae Dendropanax arboreus Food, ornamental, forage, medicine
Arecaceae Acrocomia mexicana Food Attalea cohune Food, construction, medicine Chamaedora spp. Food
Low
land
s
Cryosophila stauracanhta Construction. medicine Sabal morrisiana Construction
Bignoniaceae Tabebuia rosea Medicine, timber, ornamental Bombacaceae Ceiba pentandra Medicine, timber, ritual Quararibea Food Pseudobombax Ritual
Boraginaceae Cordia sp. Food, medicine
200
Appendix 3.1. continued Pollen taxa
VB Genus Family Associated plant taxon/taxa Uses
Brosimum Moraceae Brosimum alicastrum Food, medicine, forage, ritual Celtis Ulmaceae Celtis iguanaea Food Combretaceae Combretum Melastomataceae Clidemia Euphorbiaceae Cnidoscolus aconitifolius Food Manihot esculenta Food, medicine Fabaceae Lonchocarpus castilloi Ritual
Pachyrhizus erosus Food Phaseolus lunatus Food Mimosa Fabaceae Mimosa spp. Medicine, fuel Malpighiaceae Byrsonima crassifolia Food, medicine, apiculture L
owla
nds
Moraceae Castilla elastica Latex Pseudolmedia spuria Food
Myrsinaceae Myrsine sp. Myrtaceae Psidium guayaba Food Pimienta dioica Food
Pachira Bombacaceae Pachira aquatica Food, medicine, construction Piper Piperaceae Piper amalago Medicine
Psychotria Rubiaceae Psychotria chiapensis Medicine Rubiaceae Alseis yucatanensis Wood
Hamelia axillaris Medicine
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Appendix 3.1. continued
Pollen taxa VB Genus Family Associated plant taxon/taxa Uses
Salvia Lamiaceae Salvia coccinea Sapium Euphorbiaceae
Sapotaceae Crysophyllum mexicanum Food, medicine Manilkara zapota Food, medicine, latex Pouteria campechiana Food Solanaceae Solanum Food, medicine, forage, ritual L
owla
nds
Cestrum Medicine, ornamental Capsicum Food Trema Ulmaceae Trema micrantha Food Ulmaceae
Verbenaceae Vitex gaumeri Ornamental, fuel, forage, construction
LRF Spondias Anacardiaceae Spondias mombin, S. purpurea, S. radlkoferi Medicine, construction, food
Bursera Burseraceae Bursera simaruba Medicine, ritual Burseraceae Protium copal1 Ritual LRF-LMRF Cecropia Cecropiaceae Cecropia sp. Medicine, timber Terminalia Combretaceae Terminalia amazonia Construction
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1 Important plant for ancient and modern Maya, but not found in the pollen record. Appendix. 3.1. continued.
Pollen taxa VB Genus Family Associated plant taxon/taxa Uses
LMRF Inga Fabaceae Inga spp. Hedyosmum Chloranthaceae Hedyosmum mexicanun Food LMRF-MCF Myrica Myricaceae Myrica cerifera Medicine* Quercus Fagaceae Quercus sp. Fuel MMF Abies Pinaceae Abies guatemalensis MMF-SAF Alnus Betulaceae Alnus acuminata,
A, jorullensis
Ericaceae Arbutus sp,Cavendishia guatemalensis
Conifer6 Pinaceae Ritual Pinales Pinaceae Ritual Pinus Pinaceae Pinus caribaea, P. oocarpa Ritual
Hig
hlan
ds
Urticaceae Phenax, Pilea, Urera, Urtica Medicine
203
Appendix 3.1. continued
Pollen taxa
Genus Family Associated plant taxon/taxa Uses
Alternanthera Amaranthaceae Alternanthera sp. Amaranthaceae Amaranthus Food Chenopodiaceae Chenopodium ambrosioides Food Asteraceae2 Medicine* Cyperaceae Cyperus esculentus Food Eleocharis caribaea Peperomia Piperaceae Piperaceae Poaceae Food Polygonum Polygonaceae Food Zea Poaceae Zea mays Food Trilete spores Monolete spores
Microgramma lycopodioides, Acrostichum aureum Food
2 Uncertainty about native plant taxa
204
POLLEN TYPE P4 P4-1 P4-2 P4-3 P4-4 P4-5 P4-6 P4-7 P4-8 P4-9 P4-10 P4-11 P4-12 P4-13 P4-14 P4-15 P4-16 P4-17 P4-18Abies 4 5 3 1 0 8 0 0 0 0 0 0 0 0 0 0 0 0 0Alnus 0 0 1 1 0 1 1 0 0 1 1 0 0 1 0 0 0 0 0Hedyosmum 6 7 10 16 4 12 13 1 1 4 1 1 4 6 7 3 2 4 0Ilex 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0Myrica 2 5 1 0 1 3 0 0 0 2 1 4 3 3 6 5 5 1 1Pinus 11 72 54 62 56 53 21 1 7 4 6 8 6 12 9 4 9 14 17Quercus 17 9 5 1 2 2 6 1 2 1 4 1 11 5 4 3 6 7 4Alternanthera 5 4 11 30 21 20 0 0 0 0 0 0 0 0 0 0 0 0 0Amaranthaceae/Chenopodiaceae 0 13 11 13 10 29 5 15 13 17 10 6 23 22 14 18 14 15 21Asteraceae 12 45 77 59 50 60 138 44 88 81 62 83 83 88 111 139 145 162 151Poaceae 15 21 29 10 56 8 5 2 8 41 11 12 5 10 4 11 16 29 7Zea 2 0 1 0 1 0 5 3 0 0 3 4 4 5 1 2 2 0 1Alchornea 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0Arecaceae 0 4 5 0 0 2 0 0 3 7 0 0 1 0 0 3 3 1 1Brosimum 0 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0Bursera 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Combretaceae/Melastomataceae 0 0 0 3 0 0 0 0 0 1 0 0 0 0 0 0 0 0 2Celtis 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Malphigiaceae 0 0 0 0 0 2 0 0 1 0 0 0 0 1 0 0 0 0 0Myrtaceae 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Pollen sum 101 222 217 206 206 208 202 70 128 172 99 135 142 156 157 194 210 237 205Cyperaceae 54 159 452 458 462 471 150 20 176 270 63 90 58 48 62 109 74 158 76Polygonum 25 35 9 8 4 8 8 3 5 13 0 16 2 2 1 5 7 4 0Trilete 20 26 46 64 50 56 83 75 54 19 16 27 15 34 23 10 28 43 23Monolete 24 35 19 141 46 67 22 29 23 9 8 7 13 17 8 15 13 5 7
Appendix 4.1. Pollen counts (raw) from P-4 core.
205
Appendix 5.1. Pollen counts (raw) from L-3 core. POLLEN TYPE L3‐0 L3‐1 L3‐2 L3‐3 L3‐4 L3‐5 L3‐6 L3‐7 L3‐8 L3‐9 L3‐10 L3‐11 L3‐12 L3‐13 L3‐14 L3‐15 L3‐16 L3‐18Abies 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0Alchornea 1 4 13 14 12 8 9 10 11 7 6 10 10 7 16 16 6 8Alnus 0 0 0 1 2 2 0 4 3 1 1 2 3 0 0 1 2 1Arecaceae 4 10 4 3 1 4 6 3 1 2 0 0 0 3 2 1 3 0Bombacaceae 1 1 0 1 0 1 1 1 1 0 1 0 0 0 3 1 0 0Brosimum 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0Bursera 0 3 4 0 0 1 4 3 0 3 1 1 2 2 1 1 1 7Caesalpinaceae 0 2 0 0 0 0 1 1 0 0 0 0 0 0 0 0 1 0Celtis 2 0 0 0 2 0 3 1 1 1 0 0 2 0 0 7 2 0Combretaceae/Melastomataceae 7 19 61 63 43 48 51 65 38 45 21 16 10 8 11 18 13 11Hedyosmum 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 1 1 2Hyeronima 0 0 8 5 4 5 8 1 4 5 0 0 0 0 1 0 0 0Ilex 21 16 17 19 17 15 17 12 7 37 9 13 9 9 11 5 9 3Malphigiaceae 2 1 0 4 5 5 4 6 6 1 3 2 3 2 1 0 1 0Myrica 10 7 10 9 13 5 5 11 3 6 6 14 8 16 21 34 18 42Myrtaceae 9 10 27 8 20 28 11 12 13 9 12 18 22 20 18 7 1 0Pinus 7 5 6 0 5 3 11 6 4 10 10 7 10 4 9 4 18 9Piper 4 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0Psychotria 7 6 6 8 3 5 8 3 5 2 1 4 6 9 17 32 1 3Quercus 4 1 4 0 2 4 0 0 0 3 0 5 3 0 4 0 1 6Rubiaceae 1 4 4 12 10 4 13 10 6 2 2 7 6 7 10 5 3 2Sapium 11 6 3 4 7 6 5 4 4 0 0 1 0 3 2 1 1 0Sapotaceae 0 0 0 3 2 2 2 1 2 2 2 2 4 3 5 1 2 0Solanaceae 15 10 20 14 21 24 13 29 37 44 30 39 37 27 45 46 43 51Spondias 3 4 1 11 9 12 16 9 7 7 3 0 3 3 5 5 4 7Terminalia 8 4 6 5 5 5 3 4 2 6 0 5 2 1 1 2 1 2Trema 3 0 0 0 1 0 0 1 1 0 0 1 0 1 2 0 1 0Amaranthaceae/Chenopodiaceae 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0Asteraceae 4 6 4 3 5 4 3 1 4 4 2 1 1 2 1 1 1 2Poaceae 1 4 3 7 8 4 2 2 6 3 4 4 2 5 0 8 6 5Zea 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0Cyperaceae 11 2 1 9 2 1 6 5 4 3 5 13 2 4 1 5 2 5Pollen sum 125 126 201 195 200 196 198 200 166 201 114 153 143 132 186 198 140 161Monoletes 24 87 57 80 72 54 56 30 31 64 50 26 18 12 16 16 55 10Triletes 3 2 6 10 8 3 8 8 9 48 97 53 63 25 11 6 38 21