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Transcript
Guide 34
Ecosystem Ecology:
Energy Flow and Nutrient Cycles
tp://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
Tertiary
consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
Sun
Environmental Material Cycling Involves TRANSFORMATION
In the water cycle it is Transformation of State
gasliquidsolid
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
Decomposers
Nutrients
available
to producers
Abiotic
reservoir
Geologic
processes
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
Gm N per day
N in plants
Kg/ha
• 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
Open ocean
125
65.0
Continental shelf
5.2
Estuary
24.4
360
5.6
1,500
0.3
Algal beds and reefs
0.1
Upwelling zones
0.1
2,500
4.7
3.0
Desert and semidesert scrub
3.5
3.3
90
Savanna
2.9
Cultivated land
2.7
Boreal forest (taiga)
2.4
Temperate grassland
1.8
Woodland and shrubland
1.7
Tundra
Tropical seasonal forest
1.5
1.3
Temperate evergreen forest
1.0
Swamp and marsh
0.4
Lake and stream
0.4
0
10
0.1
0.04
0.9
2,200
22
900
7.9
9.1
600
9.6
800
600
5.4
700
1.6
Temperate deciduous forest
0.9
500
Extreme desert, rock, sand, ice
Tropical rain forest
1.2
3.5
0.6
140
1,600
7.1
1,200
1,300
4.9
3.8
2,000
2.3
250
20
30
40
50
60
0
500 1,000 1,500 2,000 2,500
0.3
0
Key
Marine
Terrestrial
Freshwater (on continents)
(a) Percentage of Earth’s
surface area
(b) Average net primary
production (g/m2/yr)
(c)
5
10
15
20
Percentage of Earth’s net
primary production
25
• Overall, terrestrial ecosystems
– Contribute about two-thirds of global NPP and
marine ecosystems about one-third
North Pole
60N
30N
Equator
30S
60S
South Pole
180
120W
60W
0
60E
120E
180
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
10 J
100 J
1,000 J
10,000 J
1,000,000 J of sunlight
• 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
THE CARBON CYCLE
THE WATER CYCLE
CO2 in atmosphere
Transport
over land
Photosynthesis
Solar energy
Cellular
respiration
Net movement of
water vapor by wind
Precipitation
over ocean
Evaporation
from ocean
Precipitation
over land
Burning of
fossil fuels
and wood
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
Carbon compounds
in water
Higher-level
Primary consumers
consumers
Detritus
Decomposition
• 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
THE PHOSPHORUS CYCLE
THE NITROGEN CYCLE
N2 in atmosphere
Rain
Geologic
uplift
Runoff
Assimilation
NO3
Nitrogen-fixing
bacteria in root
nodules of legumes
Plants
Weathering
of rocks
Denitrifying
bacteria
Consumption
Sedimentation
Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
Nitrifying
bacteria
Nitrification
Soil
Plant uptake
of PO43
Leaching
NO2 
NH4+
Nitrifying
bacteria
Decomposition
http://www.mpi-bremen.de/Binaries/Binary135/figone.jpg
Nitrogen Cycle
http://www.physicalgeography.net/fundamentals/images/nitrogencycle.jpg
The sulfur cycle
http://www.scienceclarified.com/Oi-Ph/Oxygen-Family.html
http://www.fos.su.se/~magnuss/SinNature.png
The End