chapter 54 ecosystem ecology. from a small “closed system” to the biosphere ecosystem – all...
TRANSCRIPT
From a small “closed system” to the biosphere
Ecosystem – all the organisms living in a community, plus all the abiotic factors
with which they interact
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Energy flows through an ecosystem (energy from the sun ultimately dissipates into space as heat)
Fig. 54.2
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Chemical elements are continually recycled
Fig. 54.2
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Physical laws govern these processes
Fig. 54.2
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
1st Law of Thermodynamics: Conservation of Energy
Fig. 54.2
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Fig. 54.2
2nd Law of Thermodynamics: Energy transformation is inefficient (between trophic levels)
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Fig. 54.2
Primary producers take elements in inorganic molecules and incorporate them into organic molecules
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Fig. 54.2
Additional organic molecules are produced at other trophic levels
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow
Two principal ecosystem processes:energy flow & chemical cycling
Fig. 54.2
Organic molecules are broken down into inorganic molecules by metabolism and decomposition of detritus
Energy budgets
Gross primary production (GPP) the amount of light energy converted to chemical energy per unit time (by primary producers through photosynthesis)
Net primary production (NPP) GPP minus energy used by primary producers for respiration
NPP = GPP - R
Lake and stream
Open ocean
Continental shelf
Estuary
Algal beds and reefs
Upwelling zones
Extreme desert, rock, sand, ice
Desert and semidesert scrub
Tropical rain forest
Savanna
Cultivated land
Boreal forest (taiga)
Temperate grassland
Tundra
Tropical seasonal forestTemperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Woodland and shrubland
0 10 20 30 40 50 60 0 500 1,000 1,500 2,000 2,500 0 5 10 15 20 25
(c) Percentage of Earth’s net primary production
Key
Marine
Freshwater (on continents)
Terrestrial
5.2
0.3
0.1
0.1
4.7
3.53.3
2.9
2.7
2.41.8
1.7
1.6
1.5
1.3
1.0
0.4
0.4
125
360
1,500
2,500
500
3.0
90
2,200
900
600
800
600
700
140
1,600
1,2001,300
2,000
250
5.6
1.2
0.9
0.1
0.040.9
22
7.99.1
9.6
5.4
3.50.6
7.1
4.9
3.8
2.3
0.3
65.0 24.4
Figure 54.4
(a) Percentage of Earth’s surface area
(b) Average net primaryproduction (g/m2/yr)
Energy budgets
Different ecosystems vary in overall size (Fig. a), NPP (Fig. b), and their contributions to
total NPP on Earth (Fig. c)
Lake and stream
Open ocean
Continental shelf
Estuary
Algal beds and reefs
Upwelling zones
Extreme desert, rock, sand, ice
Desert and semidesert scrub
Tropical rain forest
Savanna
Cultivated land
Boreal forest (taiga)
Temperate grassland
Tundra
Tropical seasonal forestTemperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Woodland and shrubland
0 10 20 30 40 50 60 0 500 1,000 1,500 2,000 2,500 0 5 10 15 20 25
(c) Percentage of Earth’s net primary production
Key
Marine
Freshwater (on continents)
Terrestrial
5.2
0.3
0.1
0.1
4.7
3.53.3
2.9
2.7
2.41.8
1.7
1.6
1.5
1.3
1.0
0.4
0.4
125
360
1,500
2,500
500
3.0
90
2,200
900
600
800
600
700
140
1,600
1,2001,300
2,000
250
5.6
1.2
0.9
0.1
0.040.9
22
7.99.1
9.6
5.4
3.50.6
7.1
4.9
3.8
2.3
0.3
65.0 24.4
Figure 54.4
(a) Percentage of Earth’s surface area
(b) Average net primaryproduction (g/m2/yr)
Energy budgets
Terrestrial ecosystems contribute about 2/3 and marine ecosystems about 1/3 of global NPP
Energy budgets
Resources limit primary production (just as they limit population growth)
Resources = light, water, nutrients
Figure 54.7
For example, large-scale manipulations often demonstrate N or P limitation of NPP
Actual evapotranspiration (mm H2O/yr)
Tropical forest
Temperate forest
Mountain coniferous forest
Temperate grassland
Arctic tundra
Desertshrubland
Net
prim
ary
prod
uctio
n (g
/m2 /
yr)
1,000
2,000
3,000
0500 1,000 1,5000
Energy budgets
Figure 54.8
For example, actual evapotranspiration correlates well with NPP across biomes
Actual evapotranspiration (mm H2O/yr)
Tropical forest
Temperate forest
Mountain coniferous forest
Temperate grassland
Arctic tundra
Desertshrubland
Net
prim
ary
prod
uctio
n (g
/m2 /
yr)
1,000
2,000
3,000
0500 1,000 1,5000
Energy budgets
Figure 54.8
Actual evapotranspiration is the amount of water transpired plus evaporated (a function of water
availability and solar energy)
Plant materialeaten by caterpillar
Cellularrespiration
Growth (new biomass)
Feces 100 J33 J
200 J
67 J
Figure 54.10
Energy budgetsSecondary production is the amount of chemical energy
in consumers’ food converted to consumer biomass
Some energy at each trophic level remains
unassimilated (uneaten; not shown
in the fig.)
Plant materialeaten by caterpillar
Cellularrespiration
Growth (new biomass)
Feces 100 J33 J
200 J
67 J
Figure 54.10
Energy budgetsSecondary production is the amount of chemical energy
in consumers’ food converted to consumer biomass
Some assimilated energy is passed in waste, some is used
in respiration, and the rest is net secondary
production
In this example, <17% is used for secondary
production
Energy budgetsTrophic efficiency is the percentage of production
transferred from one trophic level to another
Tertiaryconsumers
Secondaryconsumers
Primaryconsumers
Primaryproducers
1,000,000 J of sunlight
10 J
100 J
1,000 J
10,000 J
Figure 54.11
Primary producers
only convert ~1%
of sunlight
Other trophic levels ~10% (5% to 20%)
Energy budgets
Pyramid of net production
Tertiaryconsumers
Secondaryconsumers
Primaryconsumers
Primaryproducers
1,000,000 J of sunlight
10 J
100 J
1,000 J
10,000 J
Figure 54.11
Primary producers
only convert ~1%
of sunlight
Other trophic levels ~10% (5% to 20%)
Energy budgets
Pyramid of biomass
Figure 54.12
Trophic level Dry weight(g/m2)
Primary producers
Tertiary consumers
Secondary consumers
Primary consumers
1.5
11
37809
The standing crop at each trophic level
Usually narrows from
the base upwards
Energy budgets
Pyramid of biomass
Figure 54.12
The standing crop at each trophic level
But sometimes increases upwards if
primary producers turn
over rapidly
Trophic level
Primary producers (phytoplankton)
Primary consumers (zooplankton)
Dry weight(g/m2)
21
4
Energy budgets
Pyramid of numbers
Figure 54.13
Predators tend to be larger
than prey, so pyramids of
numbers nearly always narrow
upwards
Trophic level Number of individual organisms
Primary producers
Tertiary consumersSecondary consumers
Primary consumers
3354,904708,6245,842,424
E.g., field in Michigan
Energy budgets
Pyramid of numbers
Figure 54.13
For a given amount of
grain, carnivorous humans fair worse than
vegetarians!
Trophic level
Secondaryconsumers
Primaryconsumers
Primaryproducers
Biogeochemical cycles
Organicmaterialsavailable
as nutrients
Livingorganisms,detritus
Organicmaterialsunavailableas nutrients
Coal, oil,peat
Inorganicmaterialsavailable
as nutrients
Inorganicmaterialsunavailableas nutrients
Atmosphere,soil, water
Mineralsin rocksFormation of
sedimentary rock
Weathering,erosion
Respiration,decomposition,excretion
Burningof fossil fuels
Fossilization
Reservoir a Reservoir b
Reservoir c Reservoir d
Assimilation, photosynthesis
Figure 54.16
Earth is nearly a closed system with
respect to amounts of elements (with the exception of minor
additions and losses, e.g., meteorites)
Biogeochemical cycles
Organicmaterialsavailable
as nutrients
Livingorganisms,detritus
Organicmaterialsunavailableas nutrients
Coal, oil,peat
Inorganicmaterialsavailable
as nutrients
Inorganicmaterialsunavailableas nutrients
Atmosphere,soil, water
Mineralsin rocksFormation of
sedimentary rock
Weathering,erosion
Respiration,decomposition,excretion
Burningof fossil fuels
Fossilization
Reservoir a Reservoir b
Reservoir c Reservoir d
Assimilation, photosynthesis
Figure 54.16
The general biogeochemical cycle of
an element (see fig.)
Elements cycle among pools that vary in
whether they are: (1) incorporated in organic vs. inorganic molecules,
or (2) available vs. unavailable to
organisms
Transportover land
Solar energy
Net movement ofwater vapor by wind
Precipitationover ocean
Evaporationfrom ocean
Evapotranspirationfrom land
Precipitationover land
Percolationthroughsoil
Runoff andgroundwater
THE WATER CYCLE
Key processes include
evaporation, transpiration, condensation in clouds, and precipitation
Major reservoir is the ocean
(which contains about 97% of Earth’s
water)
Figure 54.17
THE CARBON CYCLE
The largest pool is
sedimentary rock, but
turnover is very slow
Major reservoirs with “fast”
turnover include fossil fuels, soils, dissolved carbon
compounds in the oceans,
biomass, CO2
Figure 54.17
CO2 in atmosphere
Photosynthesis
Cellularrespiration
Burning offossil fuelsand wood
Higher-levelconsumersPrimary
consumers
Detritus
Carbon compounds in water
Decomposition
CO2 in atmosphere
Photosynthesis
Cellularrespiration
Burning offossil fuelsand wood
Higher-levelconsumersPrimary
consumers
Detritus
Carbon compounds in water
Decomposition
THE CARBON CYCLE
Key processes are
photosynthesis, respiration,
burning of fossil fuels, volcanoes
Figure 54.17
Rain
Consumption
Decomposition
Geologicuplift
Weatheringof rocks
Runoff
Sedimentation Plant uptakeof PO4
3
Soil
Leaching
THE PHOSPHORUS CYCLE
Key processes include
weathering of rocks and
decomposition; little cycling in
the atmosphere
Major reservoirs are sedimentary rocks, soils, oceans, and
biomass
Figure 54.17
N2 in atmosphere
Denitrifyingbacteria
Nitrifyingbacteria
NitrifyingbacteriaNitrification
Nitrogen-fixingsoil bacteria
Nitrogen-fixingbacteria in rootnodules of legumes
Decomposers
Ammonification
Assimilation
NH3NH4
+
NO3
NO2
THE NITROGEN CYCLE
Key process for N to enter an ecosystem is fixation, the conversion of N2 by bacteria (or lightning) to forms usable
by plants
Major reservoir is the
atmosphere (which is about
80% N2)
Figure 54.17
Humans have dramatically altered biogeochemical cycles and ecosystems
Figure 54.19
The Hubbard Brook, NH experiment
demonstrates the
importance of forests for
nutrient cycling Whole watersheds were
experimentally deforested or not
Humans have dramatically altered biogeochemical cycles and ecosystems
Weirs measured nutrient loss from watersheds
Figure 54.19
The Hubbard Brook, NH experiment
demonstrates the
importance of forests for
nutrient cycling
Humans have dramatically altered biogeochemical cycles and ecosystems
The Hubbard Brook, NH experiment
demonstrates the
importance of forests for
nutrient cycling
Figure 54.19
Nitr
ate
co
nce
ntr
atio
n in
ru
no
ff(m
g/L
)
Deforested
Control
Completion oftree cutting
1965 1966 1967 1968
80.0
60.0
40.0
20.0
4.0
3.02.0
1.0
0
Deforested watersheds lost nutrients at prodigious rates
Humans have dramatically altered biogeochemical cycles and ecosystems
Oxides of sulfur and
nitrogen from burning of fossil fuels
have formed sulfuric and nitric acid, which have
acidified soils
Figure 54.22
Field pH5.35.2–5.35.1–5.25.0–5.14.9–5.04.8–4.94.7–4.84.6–4.74.5–4.64.4–4.54.3–4.44.3
Humans have dramatically altered biogeochemical cycles and ecosystems
Anthropogenic CO2 is the
direct cause of global warming
and various other
manifestations of climate change
Figure 54.24
CO
2 c
on
ce
ntr
ati
on
(p
pm
)
390
380
370
360
350
340
330
320
310
3001960 1965 1970 1975 1980 1985 1990 1995 2000 2005
1.05
0.90
0.75
0.60
0.45
0.30
0.15
0
0.15
0.30
0.45
Te
mp
era
ture
va
ria
tion
(C
)Temperature
CO2
Year