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Open Access e-Journal Earth Science India- www.earthscienceindia.info Popular Issue, V (II), April, 2012, p. 1-16

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LICHENOMETRY: A TECHNIQUE TO DATE NATURAL

HAZARDS

Santosh Joshi, D. K. Upreti, Pulak Das and Sanjeeva Nayaka

Once attached to substratum their place during entire lifespan do not change.

Hence, the age of lichen is an alternate for the minimum exposure time of a

substrate to the atmosphere and sunlight…………. Lichenometry has majority of

applications from dating glacier moraines, landslides, and fluvial deposits to

calibrating the age through the formation of old monuments, buildings and other

archeological structures.

Lichens are the composite organisms which have an ability to colonize on a variety of

substrates including rock, soil, trees and man–made structures in diverse environmental conditions. The thallus of the organisms comprises of fungus and algae/cyanobacteria growing in a symbiotic association. The alpine climate is generally harsh for the common plant groups. Lichens can easily cope up with the extreme conditions of the region due to their peculiar morphological, anatomical, and physiological characteristics. The slow growing and sensitive nature of lichens can be utilized as an indicator of environmental changes, load of atmospheric fallout of metals and dating the rock surfaces on which they are growing. The slow growth of lichens is attributed to only 5–10% of algal component that fulfill the carbohydrate requirements of the thallus. Lichenometry has been a globally accepted biological technique. The global acceptance of the technique may be interpreted by different references to lichenometry in the literatures of geoscience that have shown an increase of 0.02% in 35 years (Noller and Locke 2000). It is one of the chronological tools that have appeared to estimate the elapsed time ranging from decades to millions of years by utilizing different lichen species. Lichens grow on rock surfaces at relatively uniform rates over time scales of centuries (Fig. 1). Once attached to substratum their place during entire lifespan do not change. Hence, the age of lichen is an alternate for the minimum exposure time of a substrate to the atmosphere and sunlight. It was Lord William Hamilton (1730–1803), a naturalist, who had applied botany on geological dating problems and tried to relate the density and type of vegetation cover with the age of lava flows of Vesuvius. The basic concept of lichenometry is based on the similar approach. The use of lichens growth for relative dating of the surfaces was first proposed by the botanist Knut Faegri in 1930s which was further expanded by the Austrian botanist Roland Beschel in 1950s. An observed relation of the lichen thallus size with gravestones and exposed rock surfaces after glacier retreat generated an initiative by Beschel (1950, 1957, 1958, 1959, 1961, and 1973) to anticipate the use of lichens in dating. Since then lichenometry has been applied in different denudation processes, debris flows, rockwalls and escarpments. In a country like India most of the regions are under


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palaeoclimatic reconstructions and landforms to date moraines, rockfall and fluvial deposits, continuous seismic changes and are at risk to different natural hazards due to its geodynamically active locales and unique climatic pattern. That resulted into the occurrence of disasters such as: floods, earthquakes, and landslides in different parts of the country at frequent intervals. Subsequent increase in population density, thinned out forests, unplanned urbanization, and environment degradation is consequently enhancing melting of glaciers which feed the life line rivers of India. According to WWF overview report 2005 on glaciers, Gangotri, Milam and Pindari glaciers of Uttarakhand, Bara Shigri and Chota Shigri glaciers of Himachal Pradesh, Kolhani and Machoi glaciers of Jammu and Kashmir are under continuous and rapid shrinkage. Little research has been undertaken on the nature of palaeoenvironmental changes within the high mountains of the Himalayas in northern India (Owen et al. 1996). Keeping the view in mind lichenometry comes ahead as a cost effective, easy, and more reliable biological technique to estimate the frequency of these disasters.

Lichenometry can be used to find either absolute or relative dating for a surface. As there is uncertainty in the colonization of lichens on surface due to miscellaneous environmental factors, absolute dating is hardly achieved. However using different growth size of neighbouring lichen populations to distinguish between surfaces exposed at different times, relative dates can be determined (Winchester 1984). The technique has been suggested as a method complementary to other standard techniques rather than absolute dating. It does not estimate the exact date of the surface but it is assumed that the largest individual thallus of lichen on a

Figure 1. Growth rate model for the Rhizocarpon geographicum subgenus in

Wales, UK (From Matthews and Trenbirth 2011).


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particular boulder, locality, area, and monument is a function of the approximate or the minimum date of their stabilization. The use of lichenometry may increase the level of confidence and can provide effective dating with acceptable margins of errors when applied along with other relative dating methods such as, Dendrochronology or Schmidt hammer technique. Lichenometry, hence simply based on the measurement of lichen growth is thought to be quick, effortless, and advantageous over other techniques (Fig. 2).

The technique is globally applicable because of the wide environmental tolerance of lichens and can date surfaces even less than 500 years where radiocarbon and other dating techniques are least efficient (or with ambiguous interpretation) and facing difficulties. Apart from general uncertainty on the interpretation of radiocarbon dating (Matthews 1984), variation of 14C over time, circulation of carbon content, hard water and contamination are some of the major sources of error in dating through this technique. In contrast to lichenometry which provides the minimum exposure time of surfaces, radiocarbon technique detects the maximum date of surface exposure. The accuracy in dating the surface using lichenometry is negatively correlated with colonization lag time period. The appearance of foremost lichen on bare surface after the exposure or stabilization of the surface generally may take less than 10 years to more

Figure 2: Schematic diagram showing the measurement set-up for the very large lichen

(From Matthews and Trenbirth 2011),


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than 100 years depending upon species, environmental conditions, and rock composition (Noller and Locke, 2000; Smirnova and Nikonov 1990; Porter 1981; Innes 1985a). Thus, there may be an error/deviation of maximum 100 years or more in the calibrated and exact date of the exposure, establishment or formation of substrate. In case of dating boulders, stones, pebbles and other deposits, it is presumed that they are not disturbed and are not being transported through any agency from their original place of stabilization. To overcome the uncertainty associated with transportation of substrate carrying largest lichen it would be necessary to measure a large number of thalli to acquire a normal distribution curve. The upper smooth, exposed large plane surface offers big opportunity for lichens to colonize as compared to the eroded, bleached, and small surfaces. The prevailing environmental conditions and the mineral composition of the substrate also play significant role in lichen colonization. The other necessary preconditions for the study are; individuality of the lichen thallus (not amalgamate with other neighboring thalli), bare surface (surface not preoccupied by other lichens), and constant growth rate (known or unknown) of lichen (Fig. 1). It has been investigated in various studies that the growth rate of lichen species is not constant throughout its lifespan. It is generally lesser in colonization period, increases in initial time period after colonization that gradually becomes constant after maturity and slows down until death (Armstrong 1983; Beschel 1959; Innes 1985 a, b; Hansen 2008; Gupta 2005).

The size of the lichen thallus therefore, should be large enough to be appeared as mature to calculate the average growth rate (Fig. 1). The average growth rates for crustose and foliose lichens vary from 0.5–4.0 mm and 0.5–2.0 mm per year respectively (Hale 1973; Nash 1996; Brodo et al. 2001; Purvis 2000). However, Hawksworth et al. (1995) reported annual growth rates of lichens in a range of 0.01 to 90 mm per year with maximum species of 1.0–6.0 mm/yr. Growth rate of lichens are influenced by slope aspect, elevation, pollution, lithology, substrate stability, vegetation cover, wind velocity, light intensity, shade, growing season, temperature, moisture, competition, and nutrition enrichment (Hale 1973; Nollar and Locke 2000). These microclimatic conditions conducive for the growth rate may be restricted within a locality or may be wide spread over a region. Innes (1988) and Lock et al. (1979) studied more than 50 species of lichens to find out the growth rate in different environmental conditions. There are many micro and macro lichen species that can be suggested to conduct lichenometric studies in India based on their abundant availability and broad distribution (Table 1). Along with different other species of Aspicilia, Diploschistes, Rhizocarpon, Umbilicaria, Verrucaria and Xanthoparmelia, few taxa such as Lecanora polytropa (Hoffm.) Rabenh., L. garovaglii (Körb.) Zahlbr., Lobothallia praeradiosa (Nyl.) Hafellner and species of Acarospora, Caloplaca, Candelariella,

Lecidella, Porpidia, Rhizoplaca, Stereocaulon and Usnea, also have extensive distribution range in alpine and upper temperate regions of Indian Himalayas and can be proposed for lichenometric applications in India. The yellow-green coloured crustose lichen R. geographicum

is exhaustively used taxa in India as well as in other countries due to its wide distribution, high abundance, and maximum range of dating that can last up to 9000 years (Innes, 1988; Rodbell, 1992). However, lichenometric dating range of 8000–9000 years is questionable due to rock weathering, successive glacier advances, and climate change (Winchester 2004).


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Table-1: List of lichen taxa recommended for lichenometry in India.

Taxa Growth form Substrate RaGR Distribution (India)

Aspicilia calcarea (L.) Sommerf.

crustose rock 0.24–2.3 (Winchester, 1984)

AP, HP, J and K, Sikkim, UK and WB

Dimelaena oreina (Ach.) Norm.

crustose rock (non

calcareous) 0.3 (Awasthi et al., 2005); 0.57 (Hale, 1959)

HP and UK

Diploschistes scruposus (Schreb.) Norm.

crustose rock

(siliceous), soil

0.44 (Hale, 1959)

HP, J and K, MP, Maharashtra, Meghalaya, Sikkim, TN, UK and WB

Lecanora campestris (Schaer.) Hue

crustose rock 0.12–2.3 (Winchester, 1984)

HP, J and K, Rajasthan, TN and UK

Lecanora muralis (Schreb.) Rabenh.

crustose (placoid)

rock (siliceous)

1.30 (Hakulinen, 1966); 2.14 (Winchester, 1984)

HP, J and K and UK

Lecidea atrobrunnea

(Ram. ex Lam. and DC.) Schaer.

crustose Rock

(quartzite stones)

0.1( Leonard and Rosentreter, 1994) ; 0.8 (Hansen, 2008)

HP

Lobothallia alphoplaca

(Wahlenb. ex Ach.) Hafellner

crustose (placoid)

rock 0.95–1.40 (Frey 1959); HP, J and K and UK

Physcia aipolia (Ehrh. ex Humb.) Fürnr.

foliose bark, rock 1.30 ( Hakulinen, 1966); 2.0 (Porter, 1927)

HP, J and K, Karnataka and TN

Physcia caesia (Hoffm.) Fürnr.

foliose rock, bark 0.98–2.27 (Hakulinen, 1966)

HP, J and K, Manipur, Nagaland, Rajasthan, Sikkim and UK

Physcia dubia (Hoffm.) Lettau

foliose rock, bark 2.50 (Degelius, 1964) J and K and UK

Placynthium nigrum (Huds.) S. Gray

crustose rock

(calcicolous)

0.08–1.66 (Winchester, 1984)

UK

Rhizocarpon

geographicum (L.) DC. crustose rock

0.1– 0.21 (Leonard and Rosentreter, 1994); 0.2 (Hansen, 2008); 1.0 (Chaujar, 2009b)

HP, J and K and UK

Rhizoplaca chrysoleuca (Sm.) Zopf

foliose rock 0.32–0.89 (Kevin et al., 2004)

J and K, Sikkim and UK

Umbilicaria

cylindrica(L.) Del. ex Duby

foliose rock 0.01–0.04 (Frey, 1959) Sikkim and WB

Umbilicaria virginis Schaer.

foliose rock 0.3–1.0 (Hansen, 2008) HP, J and K, Sikkim and UK

Verrucaria muralis Ach. crustose rock 0.38–1.0 (Winchester, 1984)

Kerala and TN


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Abbreviations: RaGr- Radial Growth rate; AP-Arunachal Pradesh; HP-Himachal Pradesh; J and K-Jammu and Kashmir; MP-Madhya Pradesh; TN-Tamil Nadu; UK-Uttarakhand; WB-West Bengal

Different methodologies have been implemented to achieve accuracy in the dating. Basically there are two methods to establish a growth curve i.e., direct and indirect. In direct methodology lichen measurements are taken over a period of time to acquire growth rate. Indirectly growth rate can be obtained by measuring lichen thallus on substrates of known date. According to Winchester (2004), three approaches are considered to date a surface. The first original approach developed by Beschel (1950) is based on size/age correlations of largest lichens while the other two approaches are based on population size-frequency distributions. In the original method the longest axes of largest lichens on each surface are plotted against the known age surfaces and a growth rate curve is attained from the largest size/age plots. The major drawback of this approach is that composites of several thalli may be measured as a single lichen thallus and sometimes lichen growth depends on the available surface area. To resolve the problem of anomalous thalli, an average of the largest lichens on a surface has been considered in many studies (e.g. Matthews 1974) that turn out to be more consistent (Matthews 1975; Innes 1984; 1985a). However an average will always underestimate true growth rate and therefore the dating will be too young. The other two approaches are based on the population size-frequency which reduce the uncertainties based on lichenometric assumptions and facilitate independent dating. One of the approaches given by McCarroll (1993) and Bull et al. (1994) use measurements of population of largest lichens on uniform aged surfaces to investigate the history of seismic and large diachronous surfaces (Winchester 1984). The other one developed by Winchester and Harrison (1994) utilizes the measurements of whole lichen populations (large and small thalli) growing on rock faces with similar aspect and lithology. The advantage of later is same as in both cases statistical methods can be applied and are less interrupted by anomalous

Xanthoparmelia

conspersa (Ach.) Hale foliose rock

0.55–4.95 (Armstrong, 1973); 1.60 (Hale, 1959); 7.6 (Hale, 1967); 5.30 (Phillips, 1963); 3.28 (Lawrey and Hale, 1977); 3.84 (Jones and Platt, 1969)

HP, J and K, Rajasthan and UK

Xanthoria elegans (Link.) Th. Fr.

foliose rock

0.5–0.9 (McCarthy and Smith, 1995); 1.35 (Hakulinen, 1966); 0.43–0.44 (Vitt et al., 1988)

HP, J and K, Sikkim and UK

Xanthoria parietina (L.) Th. Fr.

foliose bark, rock

0.12–3.13 (Winchester, 1984); 6.0 Honegger et

al. (1996); 2.50 (Degelius, 1964); 2.15 (Hakulinen, 1966)

HP, J and K and TN

Methodology


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thalli. But the procedures are time taking since the results require the measurements of a large number of lichens. One least accepted relative approach is the percentage lichen cover (Noller and Locke 2000). In this method ratio of the area covered by lichen thalli and the total exposed area is to be estimated. But the major drawback associated with this approach is competition and inability of lichens to grow on lateral sides due to abrasions, and is also biased to user.

In India there are many known sources through which the lichen colonization delay and

growth rate can be established. While working on or around archeological structures of known dates (such as temples, old building, roads, dams, platforms etc.) the successful dating of different seismic movements in the vicinity of these known sources can be achieved. Moreover, rate of glacier recession, river, lake and sea level formation and changes can also be frequently estimated through all the three approaches.

Applications

Lichenometry has majority of applications from dating glacier moraines, landslides, and fluvial deposits to calibrating the age through the formation of old monuments, buildings and other archeological structures (Innes 1985a). The applications of lichenometry based on different palaeoclimatic events, reconstructions and man–made artifacts can be categorized as follows: Glacier retreat

Glaciers are among the most sensitive indicator of climate change. Their recession and advancement depends on the prevailing climatic conditions. Glaciers on recession leave heaps of moraines that on steady and continuous exposure provide habitat for some lichens that are peculiar in their ecological amplitudes and are restricted to alpine localities. Lichenometry takes advantage of the lichens growing in the vicinity of the glaciers and predict the minimum time of exposure of these moraines and thereby anticipate the age of glacier retreat (Fig. 3). Subsequent to Beschel (1950, 1957, 1958, 1961, 1973), other workers such as Griffey (1977), Porter (1981), Gordon and Sharp (1983), André (1986), Werner et al. (1987), Spence and Mahaney (1988), Werner (1990), Burrows et al. (1990), Rodbell (1992), Matthews (1994), Winchester and Harrison (1994), Smith et al. (1995), Harrison and Winchester (2000), Smith and Desloges (2000), Sancho et al. (2001), Solomina and Calkin (2003) and Armstrong (2005) had applied the technique on glacial deposits in different countries. Forman et al. (2007) used lichenometry to estimate the age of recently exposed moraines close to the Inland Ice. Hansen (2008) outlined and discussed the different applications and field methods which may result in lichen growth curves (Fig. 4) and lichenometric dating curves. The mountains of the western and central Himalayas and Karakoram comprises of greatest concentration of glaciers outside the Polar Regions (Owen et al. 1996).


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Figure 3. Location of lichen measurement transects at Tiedemann Glacier,

Canada. Lichens were measured along eight transects (From Larocque and Smith

2004)


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The high terrain of Jammu and Kashmir, Himachal Pradesh, Uttarakhand and few states of Eastern Himalaya constitute the major proglacier regions of Indian Himalayas. This makes the Indian Himalayas particularly important in understanding environmental changes with reference to the nature and timing of glacier fluctuations. Studies on Indian glaciers recently gain prolific attention due to increase in earth temperature (global warming). In India, lichenometric studies were first carried out in the Gangotri glacier area of Uttarakhand by Srivastava et al. (2001). Since then only few studies on proglacier valleys have been accomplished. Awasthi et al. (2005) carried out studies on Gangotri glacier valley using lichenometry (with Dimelaena oreina) and Schmidt hammer techniques simultaneously. Based on the known age of two moraines, the relative ages of the other two unknown moraines have been calculated. According to the study, both the techniques are negatively correlated to each other since the size of the lichen thallus (lichen growth) increases with time, whereas in the Schmidt Hammer method R-values decreases with time because the intensity of rock weathering increases with time. Chaujar (2009b) studied the glacier activities in Chorabari and Dokriani glacier of Garhwal Himalayas in Uttarakhand. The study revealed the climate change and its impact on the Himalayan glaciers based on the dating of lichens, growing on loops of moraines formed due to advancement and recession of the Chorabari glacier. According to the investigation, the Chorabari glacier started receding 258

Figure 4. Comparative graph of lichen growth curves developed at various study

sites (From Larocque and Smith 2004)


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years ago from the point of its maximum advancement. The study gains the support of Kedarnath temple situated nearer to the snout of the glacier. Earlier Chaujar (2009a) has estimated the age of retreat in the Dokriani Bamak glacier about 314 years.

Recently, two of the present authors (Joshi and Upreti 2010) (Fig. 5) have attempted to

estimate the minimum age of exposure of the moraines near Pindari glacier, based on the known growth rate (0.2mm/year) of the lichen Rhizocarpon geographicum (L.) DC. The lichen species has already been calibrated many times for its average growth rate by different glaciologist and geologist in alpine regions in different parts of world. The simple analyses of 1 km sampling unit beyond glacier snout lead to conclude that the area has certainly been exposed before 600 years ago. Outcome of the study suggested that the time taken by the glacier to recede from one kilometer distance to its present position is approximately or a minimum of 600 years. The study was performed in a short duration with simple methodology of distance/size/age correlations since previous data on glacier retreat and aerial photographs were not available during the study.

Figure 5. Rhizocarpon geographicum (L.) DC., a widely used lichen species in

lichenometry; Diagrammatic representation of lichenometric study performed in the

vicinity of Pindari Glacier by two of the authors (From Joshi and Upreti 2010).


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Landslides and Earthquakes

Landslides are one of the most detrimental threats in Indian Himalayas. According to Sarkar and Kanango (2010), the major cause of the landslide is an unprecedented heavy rainfall more often known as cloudburst. The changed land use pattern due to increase in anthropogenic pressure in the mountain areas poses threat of different hazards including landslides that leads to significant loss of property, resources, and lives. The Himalayas being the highest mountain chain on the earth are marked by unstable boulder stage of rivers and streams, very high relief, and intense erosion activity. Some preliminary factors, like deforestation, construction of dams and roads, mining, unplanned urbanization and intervention in natural drainage, may in due course become the triggering factor and start the landslide. In some other cases, geological or climatic events like earthquakes or rainstorms initiate the movement (Singh 2009). Human activity like construction of roads can have a major impact on the vulnerability of a mountain slope. Landslides occur frequently and without any warning causing catastrophe. Regardless of uncertainty, the magnitude of these incidents, susceptible areas, the time period of such disasters and their potential impact can be studied, analyzed and evaluated on the basis of past occurrences and existing knowledge to reduce their impact (Singh 2009). Data base along with satellite pictures and old maps hold valuable information pertaining to the succession of landslides. However, in absence of historical data, absolute dating of ancient landslides provides the only means of determining their distribution in time (Lang et al. 1999). Lichenometry may find some applications in estimating the magnitude of palaeolandslides through relative dating. The lichenometric technique is applied on the lichens inhabiting stable long standing material. The application of lichenometry on mass movements is essential to understand the date, frequency, and intensity of the hazards. Evaluation of sequel of different prehistoric landslides in particular region helps in anticipating the stability of the land and predicting the future disasters in the area. Lichenometry may be a well implemented palaeoseismic practice for describing the extent and intensity of seismic shaking caused by prehistoric earthquakes (Bull 2003). The geomorphic consequences of debris flows and their associated storms have been documented in many parts of the world. Nikonov and Shebalina (1979) studied the historic earthquakes in Tadjikistan by directly estimating the age of landslide with the help of lichen Lecidea lactea. Kaatz (1998) and Reynolds (2001) studied the landslides near river gorge in different parts of Washington (USA). Winchester and Chaujar (2002) carried out lichenometric dating of slope movements in Nant Ffrancon, North Wales. Bull (1996) and Bull and Brandson (1998) in New Zealand applied this technique to establish discrete pulses of rock fall material related to coseismic activity. Bull et al. (1994) confirmed the age of the earthquakes in San Andreas with the help of rockfall events occurred in distant places in Sierra Nevada of California. After comparing the times of San Andreas Fault earthquakes and lichenometry age estimates for rockfall events at seven sites, the causative factors for regional rock fall events in the Sierra Nevada has been envisaged which were found to be distant earthquakes on the northern and southern San Andreas Fault as well as local earthquakes. Cross checks in the study included four species of lichens (Acarospora

chlorophana, Rhizocarpon subgenus rhizocarpon, Lecanora sierrae, Lecidea atrobrunnea). Gupta (2005) in India studied the Pawari landslide zone in Kinnaur district of Himachal

Pradesh. The study was based on the percentage cover of lichens on slided material (boulders,


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pebbles etc.). The investigation implies that boulders (in debris) containing more lichen cover are more stable compared to the ones showing lesser lichen cover. Slopes covered with more or less fresh rock boulders and pebbles in the slide zone indicate an active part within the slided mass. The work provides an indirect methodology to assess the differential movement of slope within the slide mass. In the study, any specific species of lichen is not taken into account, however, the correlation of size and presence or absence of lichens on boulders in different zones are well documented with the rate of movement. Instead of the importance of the technique in the relevant field not much significant work based on this biometric technique in India has been recognized.

Archaeological evidence for dating

The idea of using lichens on archeological remains has been aroused in the year 1939 by Renaud. Joubert et al. (1983), recommended possible use of lichenometry in dating archaeological structures where other established methods of dating are not feasible. Petroglyphs, gravestones, remains of ancient buildings and prehistoric monuments are found to be suitable for this technique as they may serve as reference standard. A German lichenologist Gerhard Follmann appears to be the first person who used lichenometry on archeological structures (Rutherford et al. 2008). Follmann in early 60’s studied the growth rate of Dirinaria

picta, Diploschistes anactinus and Lecidea paschalis and applied them to estimate the ages of Easter Island’s (Rapa Nui) monumental statues and stone platforms. The study suggested the carved period of statues centered around A.D. 1530. Winchester and Chaujar (2002) and Winchester and Sjöberg (2003) used the churchyards lichens to study the geomorpholoical events in Nant Ffrancon, North Wales, England, and beach ridge formation at Bådamalen on the North Bothnian cost, Sweden respectively.

Not much work has been conducted in determining the approximate age of manmade

buildings such as monuments, graveyards, memorial parks etc. in India as well as in other parts of the world. However, Chaujar (2006) enlightened the geological activities at four different localities of Himachal Pradesh by calculating the dates of colonization delay and growth rate of R. geographicum growing over the rocks near Kalka-Shimla railway track and in grave yards of Sanjoli, Dharamshala, and Dalhousie. The study confronts the measurements of the largest lichen thalli that were graphically plotted against the age of the monuments and line of best fit was drawn. Requirement of new calibrations for the growth rate of lichens and colonization delay in the regions that have experienced environmental changes irrelevant to distance have been emphasized. This is contrary to the statement given by Tucson (1998), Denton and Karlen (1973) and Bull et al. (1994) for minimal effect of environmental factors, such as substrate composition and texture, annual precipitation, seasonal and spatial variations and temperature regimes, on lichen colonization. Although the study critically favors the role of shade, light, and wind in enhancing the rate of lichen growth as supported by Benedict (1967), yet does not offers a complete explanation for the apparent spatial variation in R. geographicum growth trends emerging in the study area.


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Fluvial studies

Lichenometry alone or supplemented with other techniques has also been applied in the study of river systems (Macklin, 1986; Macklin et al. 1992; Merrett and Macklin 1999; Maizels and Dugmore 1985; Maas et al. 1998; Jacob et al. 2002; Gob et al. 2003; Gob et al. 2005, 2008; Keesstra et al. 2005; Thompson and Jones 1986). Lichens usually are damaged or removed due to abrasions when boulders are transported in riverbeds. Thus, the presence of lichen thalli on particles are the direct indicative of long standing positions of these particles and their stabilization period is equivalent to the lichens age. If the age of the lichens on a boulder is determined, the last mobilization of the particle can easily be dated (Gob et al. 2010). Rivers are under continuous trend of changing their directions. In areas of high altitude, lichenometry may help in depicting the time period of the differential movement of rivers from its original position. Rivers in the course of time make different tracks leaving small and large pebbles, stones and boulders in their previous paths. Eventually, the smooth surface remains occupied by lichens that can be utilized to date their stabilization in the path (Fig. 6). In this manner by measuring the largest thalli in different residual paths of river the minimum time of the exposure of surface after river divergence/tilting can be evaluated. This finally can be helped in predicting the time taken by the river from its original place to its current place of flow. The application of lichenometry in fluvial deposits was first undertaken by Gregory (1976), who used it to date flood limits and river capacity based on lichens present on bedrock and river banks. The successive deposition of sediments, terraces and alluvial fans have been dated with the help of R. geographicum (Harvey et al. 1984; Macklin et al. 1992; Maas et al. 1998). The

Figure 6. Some common lichens for lichenometry study in India; a) Acarospora sp.,

b) Dimelaena oriena, c) Lobothallia praeradiosa; d) and e) Fluvial deposition in

Goriganga river of Milam valley (Uttarakhand).


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application of the technique has also been used in signifying the sequence of palaeofloods (Maas et al. 2001). Christiansen et al. (2002) used lichenometry in reconstructing the Holocene environment from deltaic deposits in northeast Greenland. Gob et al. (2003) used the technique in Figarella river catchment in France. The dating was performed on lichens present on terrace pebbles to determine the period of their deposition or terrace formation and incision of the river. According to the study the Figarella underwent three major incision phases. The highest level of 20–25 m did not have any lichen colonization and was inhabited by high, dense scrub. The maximum lichen size below 12 m of terrace was 11cm that envisaged the age of the terrace formation about 1800 years. This lead to conclude that the river began to incise and transform the pebble sheets in the terrace about 2000 years ago. The third level was at 3 m and represented by largest thalli size of 7 cm that indicates 400 years old terrace level. The study also highlighted the relation of boulder transportation with palaeofloods. The presence of largest lichen thalli on riverbed boulders indicated the longevity of their stable conditions. That in turns gave an idea of the last or ancient flood occurrences. Gob et al. (2010) found out the specific stream power of flood event to be more than 60 years old. The study included four riverbeds in southern part of France. In the study lichenometry was applied in dating the last mobilization of blocks with lichens in the rivers, and thresholds of sediment transport based on sediment size were determined. According to the study the sediment thresholds may vary within the same type of rivers and the specific stream power required to transport particle of a given diameter may vary by up to 10 times from one river to next. Such types of studies in Indian subcontinent have not been initiated. Volcanoes

An interesting and rather unnoticeable application of lichenometry is to date the prehistoric eruption of volcanoes in a particular landscape. On account of high tolerance, lichens can survive in extreme conditions of heat. Many lichens such as Caloplaca crosbyae, Dirinaria

aegialita, D. applanata, Candelariela concolor, Ramalina umbilicata, Hyperphyscia adglutinata, Syncesia and Xanthoparmendia sp. are known to grow on magma (Jorge-Villar and Edwards 2009). After calibrating the growth rate and size of the lichen thalli (diameter or length) a graph can be plotted against the age of the substratum (volcanic emission). The technique will be highly useful in continents prone to volcanic explosions. In India volcanic activities are rare however frequency and intensity of the ancient volcanic explosions can be calibrated in certain American, European, and Asian countries and in that way future eruption can be predicted in a more simple way through lichenometry.

In addition to these the technique may also be applicable in sea level changes, lake levels,

solifluction, weathering and climatic variation (Beschel 1961).


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Conclusion and Perspectives

Where the other surface dating tools such as radiocarbon dating, dendrochronology and weathering based techniques face difficulties, lichenometry appears to succeed and has gained prolific attention due to simple methodology but it has some restrains as well. Species identification in the field, influence of environmental factors on growth rate, nature and timing of colonization (colonization delay), absence of reproducibility in many published sampling designs, the supposed inadequacy of a single parameter as an index of age, difficulties associated with the methodology of growth rate determination are some of the drawbacks in the implementation of lichenometry (Worsley 1981). However, as the technique is widely used in relative or approximate dating its role in tectonic, geomorphic, geo-chronological studies and in other landform evolutions cannot be overlooked. In India the lichenometry has been initiated in the initial years of the last decade. But lack of valuable information in the study sites in favor of palaeoclimatic conditions and surfaces to date, are the major problems in application of the technique in India. Acknowledgements: Authors are thankful to Director, National Botanical Research Institute (CSIR-NBRI), Lucknow for providing laboratory facilities and Ministry of Environment and Forests, New Delhi for financial assistance.

Further Readings:

Armstrong, R. A. (2005) Radial growth of Rhizocarpon section Rhizocarpon lichen thalli over six years at

Snoqualmie Pass in the Cascade Range, Washington State. Arctic, Antarctic and Alpine Research, v. 37, pp. 411–415.

Awasthi, D. D., Bali, R. and Tewari, N. K. (2005) Relative dating of moraines by lichenometric and Schmidt Hammer techniques in the Gangotri Glacier valley, Uttarkashi district, Uttaranchal. Special Publication of the Palaeontological Society of India, v. 2, pp. 201–206.

Benedict, J. B. (2009). A review of Lichenometric dating and its applications to archaeology. American antiquity, v. 74 (1), pp. 143–172.

Beschel, R. E. (1973) Lichens as a Measure of the Age of Recent Moraines. Arctic and Alpine Research, v. 5, pp. 303–309.

Chaujar, R. K. (2006) Lichenometry of yellow Rhizocarpon geographicum as data base for the recent geological activities in Himachal Pradesh. Current Science, v. 90 (11), pp. 1552–54.

Gupta, V. (2005) Application of lichenometry to slided materials in the Higher Himalayan landslide zone. Current Science, v. 89(6), pp.1032–1036.

Jorge-Villar, S. E. and Edwards, H. G. M. (2009) Lichen colonization of an active volcanic environment: a Raman spectroscopic study of extremophile biomolecular protective strategies. J. Raman Spectrosc., v. 41, pp. 63–67.

Joshi, S. and Upreti, D. K. (2010) Lichenometric studies in vicinity of Pindari Glacier in the Bageshwar district of Uttarakhand, India. Current Science, v. 99(2), pp. 231–235.

Larocque, S. J. and Smith, D. J. (2004) Calibrated Rhizocarpon spp. Growth Curve for the Mount Waddington Area, British Columbia Coast Mountains, Canada, Arctic, Antarctic, and Alpine Research, v. 36 (4), pp. 407-418.

Matthews, J. A. and Trenbirth, H. E. (2011) Growth rate of very large crustose lichen (Rhizocarpon subgenus) and its implications for lichenometry. Geografiska Annaler, Series A, Physical Geography, v. 93, pp. 27-39.

Sarkar, S. and Kanungo, D. P. (2010) Landslide disaster on Berinag–Munsiyari Road, Pithoragarh District, Uttarakhand. Current Science, v. 98(7), pp. 900–902.


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Singh, A. K. (2009) Causes of slope instability in the Himalayas. Disaster Prevention and Management, v. 18(3), pp. 283–298.

Vitt, D. H., Marsh, J. E. and Bovey, R. B. (1988) Mosses, Lichens and Ferns of Northwest North America (Lone Pine Publishing: Edmonton) 296 p.

About the Authors

Santosh Joshi*, D. K. Upreti, Sanjeeva Nayaka belong to Lichenology Laboratory, National Botanical Research Institute,(Council of Scientific and Industrial Research) Rana Pratap Marg, Lucknow (UP) – 226 001, India

Pulak Das belongs to Dept. of Ecology and Environmental Science, Assam University, Silchar-788011

*Corresponding author Email: [email protected]

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