Guide 34 Ecosystem Ecology:

Energy Flow and Nutrient Cycles

http://www.mordantorange.com/blog/archives/comics_by_mike_bannon/mordant_singles/0511/

Overview: Ecosystems, Energy, and Matter

An ecosystem consists of all the organisms living in a community As well as all the abiotic factors with which they interact

Regardless of an ecosystem’s size

Its dynamics involve two main processes:

Energy Flow and Chemical Cycling

Energy flows through ecosystems

While matter cycles within them

• Energy flows through an ecosystem

– Entering as light and exiting as heat

Microorganisms

and other

detritivores

Detritus

Primary producers

Primary consumers

Secondary

consumers

Tertiary

consumers

Heat

Sun

Key

Chemical cycling

Energy flow

Environmental Material Cycling Involves TRANSFORMATION

In the water cycle it is Transformation of State

gasliquidsolid

In chemical cycles (C, N, P, S) it is Transformation in Redox

State

http://www.wou.edu/las/physci/GS361/Energy_From_Fossil_Fuels.htm

The major Chemical Transformations in the Environment

are carried out by microorganisms – and on a global

scale, very large amounts are transformed every year.

Recent increases in

anthropogenic N fixation

in relation to “natural” N

fixation. Modified from

Vitousek, P. M. and P. A.

Matson (1993)

1 Tg = 1 X 109 kg

Microorganisms can

make a “living” off of

the energy available

in the Electron Tower

A General Model of Chemical Cycling

• All elements

– Cycle between organic and inorganic reservoirs

• Gaseous forms of carbon, oxygen, sulfur, and nitrogen

– Occur in the atmosphere and cycle globally

• Less mobile elements, including phosphorous, potassium, and calcium

– Cycle on a more local level

• The carbon cycle

– Reflects the reciprocal processes of photosynthesis and cellular respiration

Decomposition and Nutrient Cycling Rates

• Decomposers (detritivores) play a key role – In the general pattern of chemical cycling

Consumers

Producers

Nutrients

available

to producers

Abiotic

reservoir

Geologic

processes

Decomposers

GtC – Giga Tons Carbon - One Billion Tons of Carbon

In considering material flow through an environment

Two Factors need to be considered:

Pool Size (Compartment Size) BOXES

Flux – gain or loss to the pool over some period of time

ARROWS

N in plants

Kg/ha

Gm N per day

• Net primary production (NPP)

– Is equal to Gross primary Production (GPP) minus the energy used by the primary producers for respiration

• Only NPP

– Is available

– to consumers

http://sciencebitz.com/?page_id=204

• Different ecosystems vary considerably in their net primary production – And in their contribution to the total NPP on Earth

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 forest

Temperate 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

Percentage of Earth’s net

primary production

Key

Marine

Freshwater (on continents)

Terrestrial

5.2

0.3

0.1

0.1

4.7

3.5

3.3

2.9

2.7

2.4

1.8

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

1,200

1,300

2,000

250

5.6

1.2

0.9

0.1

0.04

0.9

22

7.9

9.1

9.6

5.4

3.5

0.6

7.1

4.9

3.8

2.3

0.3

65.0 24.4

Percentage of Earth’s

surface area

(a) Average net primary

production (g/m2/yr) (b) (c)

• Overall, terrestrial ecosystems

– Contribute about two-thirds of global NPP and marine ecosystems about one-third

180 120W 60W 0 60E 120E 180

North Pole

60N

30N

Equator

30S

60S

South Pole

Trophic Relationships

• Energy and nutrients pass from primary producers (autotrophs)

– To primary consumers (herbivores) and then to secondary consumers (carnivores)

Trophic Efficiency – Is the percentage of production transferred from

one trophic level to the next

– Usually ranges from 5% to 20%

http://www.esf.edu/efb/schulz/fattyacid.html

Pyramids of Production • This loss of energy with each transfer in a food chain

– Can be represented by a pyramid of net production

Tertiary

consumers

Secondary

consumers

Primary

consumers

Primary

producers

1,000,000 J of sunlight

10 J

100 J

1,000 J

10,000 J

• The dynamics of energy flow through ecosystems

– Have important implications for the human population

• Eating meat

– Is a relatively inefficient way of tapping photosynthetic production

• Worldwide agriculture could successfully feed many more people

– If humans all fed more efficiently, eating only plant material

Trophic level

Secondary

consumers

Primary

consumers

Primary

producers

Food webs: complexes of feeding relationships

A food web refers to all the trophic (feeding)

connections among species within a community.

http://www.sltec.com.au/sltec/products_liqfert_sustain_n_gro.html

Biogeochemical Cycles

Transport

over land

Solar energy

Net movement of

water vapor by wind

Precipitation

over ocean Evaporation

from ocean

Evapotranspiration

from land

Precipitation

over land

Percolation

through

soil

Runoff and

groundwater

CO2 in atmosphere

Photosynthesis

Cellular

respiration

Burning of

fossil fuels

and wood Higher-level

consumers Primary

consumers

Detritus Carbon compounds

in water

Decomposition

THE WATER CYCLE THE CARBON CYCLE

• Water moves in a global cycle

– Driven by solar energy

Water Movement is a major force in Geological Change

Wadi Zin

The nitrogen cycle and the phosphorous cycle

N2 in atmosphere

Denitrifying

bacteria

Nitrifying

bacteria

Nitrifying

bacteria

Nitrification

Nitrogen-fixing

soil bacteria

Nitrogen-fixing

bacteria in root

nodules of legumes Decomposers

Ammonification

Assimilation

NH3 NH4+

NO3

NO2

Rain

Plants

Consumption

Decomposition

Geologic

uplift

Weathering

of rocks

Runoff

Sedimentation Plant uptake

of PO43

Soil

Leaching

THE NITROGEN CYCLE THE PHOSPHORUS CYCLE

http://www.mpi-bremen.de/Binaries/Binary135/figone.jpg

http://www.physicalgeography.net/fundamentals/images/nitrogencycle.jpg

Nitrogen Cycle

http://www.scienceclarified.com/Oi-Ph/Oxygen-Family.html

The sulfur cycle

http://www.fos.su.se/~magnuss/SinNature.png

The End