Chapter 54 Ecosystem Ecology. From a small “closed system” to the biosphere Ecosystem – all the organisms living in a community, plus all the abiotic

Chapter 54

Ecosystem Ecology

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


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


Chemical elements are continually recycled

Fig. 54.2


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


Physical laws govern these processes

Fig. 54.2


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


1st Law of Thermodynamics: Conservation of Energy

Fig. 54.2


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


Fig. 54.2

2nd Law of Thermodynamics: Energy transformation is inefficient (between trophic levels)


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


Fig. 54.2

Primary producers take elements in inorganic molecules and incorporate them into organic molecules


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


Fig. 54.2

Additional organic molecules are produced at other trophic levels


detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


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


Weirs measured nutrient loss from watersheds

Figure 54.19


demonstrates the


nutrient cycling



demonstrates the


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


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


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

Documents

Chapter 54 Ecosystem Ecology. From a small “closed system” to the biosphere Ecosystem – all the organisms living in a community, plus all the abiotic