Outline

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Outline What is ecosystem ecology? What
questions are pursued? What is the history of
ecosystem ecology? What approaches are commonly
used?
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What is an ecosystem?
Tansley (1935)
". . . the whole system including not only the
organism-complex, but also the whole complex of
physical factors forming what we call the
environment of the biome . . . . the basic
units of nature on the face of the earth.
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Ecosystem Ecology
Communities Primary Producers Consumers Species
Wind Currents Thermal Flux Geochemistry
Biological
Physical / Chemical
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Linking chemistry and biology Biogeochemistry N
utrients, primary producers and consumers
C P Ratio
Light
Primary Producers
Carbon (C)
Phosphorus (P)
Copepods
Daphnia
Nutrients
CP Ratio
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Types of Questions
Study the fluxes, transformations, and
interactions of carbon, nutrients, and energy
(biogeochemistry) Identify the sources and fate
of primary production Autocthonous (from
within) Allocthonous (from outside) Understand
the processes that regulate and change ecosystem
structure Identify the controls on primary
production
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Key Players in the development of ecosystem
ecology Stephen Forbes The lake as a
microcosm Consider the entire habitat as one
entity
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Stephen Forbes. 1887. The lake as a microcosm
Hydrology Geochemistry Zooplankton Microbes Phytop
lankton Fishes Etc.
Keyed the transition from nineteenth-century
natural history to twentieth-century ecological
science
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Key Players in the development of ecosystem
ecology Stephen Forbes The lake as a
microcosm Consider the entire habitat as one
entity Arthur Tansley Plant ecologist, coined
the term ecosystem Lindeman Trophic-dynamic
aspect of ecology
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Raymond Lindemans Legacy
Lindeman, R. L. 1942. The trophic-dynamic aspect
of ecology. Ecology 23 399-418.
"Here we search the placid waters, Find a
microcosmic sea Wherein hunting, hunted microbes
Eat and live and die, as we ... Dynamic worlds
are set before us, Let us humbly seek to learn."
1915-1942
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Furthered the idea of studying systems from the
perspective of energy What are the energetic
linkages within an ecosystem?
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Some Key Concepts From Lindeman
-- ... organisms within an ecosystem may grouped
into discrete trophic levels
The Trophic Level Concept
-- The more remote an organism is from the
initial source of energy, the less probable that
it will be dependent solely upon the preceding
trophic level as a source of energy Trophic
Omnivory
-- The progressive energy relationships ...of an
Eltonian Pyramid may be epitomized in terms of
..productivity Productivity, not biomass, is
reduced as one moves up the food web
Trophic Level
Production
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Key Players in the development of ecosystem
ecology Stephen Forbes The lake as a
microcosm Consider the entire habitat as one
entity Arthur Tansley Plant ecologist, coined
the term ecosystem Lindeman Trophic-dynamic
aspect of ecology Arthur Hasler, Gene Likens,
David Shindler The foundations of experimental
ecosystem ecology Eugene Odum, C.S. Holling
Theories of ecosystem development and change
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• Approaches Commonly Adopted
• Experimentation
• Long-term Study
• Comparative study
• Modeling
• Estimation

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Experimentation

• Scaling issues
• Pioneering work by Arthur Hasler the reference
  system
• Hubbard Brook Experimental Forest

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Scaling Issues in Ecosystem Experiments
Measuring Primary Production
Primary Production
6 CO2 12 H2O ( sunlight) --gt C6H12O6 6 O2
6 H2O
Respiration
C6H12O6 6 O2 6 H2O -gt 6 CO2 12 H2O Energy
At least two approaches
Measure O2 release Measure CO2 uptake using a
radioactive tracer (14CO2)
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Using Radiolabelled C
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Problem adsorption onto organic particulates
Time
organic particles
Filter
Passes through filter
sticks to filter
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Solution Light / Dark Bottle Method
14C02 - Light
14C02 Light
Dark Bottle
Light Bottle
Primary production Adsorption
Adsorption
Use the difference between light and dark bottles
to estimate uptake by producers
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Problems in extrapolating to whole ecosystems
Duration of Incubation
6 14CO2 12 H2O ( sunlight) --gt C6H12O6 6 O2
6 H2O
C6H12O6 6 O2 6 H2O -gt 6 14CO2 12 H2O
Energy
Eventually, labeled carbon will be released back
into the inorganic state
CO2 limitation In closed bottles under high
light and nutrients, carbon can become the
limiting factor
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More problems in extrapolating to whole ecosystems
water surface
Light
These bottles typically show reduced primary
production Assumed to be due to photoinhibition
in situ measurements String bottles across depth
gradient
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More problems in extrapolating to whole ecosystems
water surface
These bottles typically show reduced primary
production Assumed to be due to photoinhibition
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Scaling Issues in Ecosystem Experiments
The Eutrophication Controversy
Eutrophication Condition characterized by high
algal production (often noxious species such as
cyanobacteria)
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The Nutrient Bioassay and the Eutrophication
Controversy
C
N
P
Spike bottles with C, N, or P, and measure
response (usually chlorophyll)
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The Nutrient Bioassay and the Eutrophication
Controversy
C
N
P
Response
This would suggest Carbon limitation
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Problems in interpreting bottle bioassay
experiments
They tell you what is limiting, but not why A
high P lake will show a response to C input in a
bottle, because water in the bottle, sealed from
the atmosphere, is C-limited
N
P
P
C
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Large-Scale Experiment Resolved the Debate
Experimental Lakes Area, Ontario Canada-
C, N
C, N, P
Lake 226
David Schindler and Colleagues
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Experimentation
Scaling issues Pioneering work by Arthur
Hasler the reference system Hubbard Brook
Experimental Forest
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Arthur Haslers Hypothesis Lake productivity in
dark-stained lakes is limited by low light
Therefore, if one could add lime to a lake, one
would increase pH, alter dissolved organic
carbon chemistry increase light
environment increase primary production
Light
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Paul Lake
Permanent Dike
Peter Lake