The ecosystem concept

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Month Day Topic
Aug.
26
Introduction
28
The ecosystem concept
Sept.
2
Climate/soils
4
Soils II
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Energy and water
balance
11
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16
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Ecosystem Ecology
Study of interactions among
organisms and their physical
environment as an integrated system
What is an ecosystem?
bounded ecological system consisting
of all the organisms in an area and
the physical environment with which
they interact
The ecosystem concept
Ecological succession
Trophic dynamics
Biogeochemistry
1. Ecological succession
The Midwestern botanists
Henry Cowles (1869-1939), U. of Chicago
1. Vegetation changes in time in
response to stress
2. Orderly development against
backdrop of unpredictable physical
disturbance
3. Plant communities are dynamic;
ever-changing…
Frederic Clements (1874-1945),
U of MN and Carnegie Institute
1. Succession is a predictable linear
process to a climax community
2. Community is analogous to an
organism; the “superorganism”
Henry Gleason (1882-1975), U of MI and NY
Botanical Garden
1. Individualistic concept of plant
communities
2. Communities are an assemblage of
organisms, not an “organismal entity”
3. Major critic of Clements
4. Bryologist!
1. Ecological succession
The Midwestern botanists
1. Plant communities are dynamic
2. Communities are analogous to
organisms -versus-
3. Communities are assemblages of
individuals
2. Trophic dynamics
The animal ecologists
Charles Elton (1900-1981), Oxford U. and the
Bureau of Animal Populations
1. Niche concept
2. Niches are linked into food chains
3. Pyramid of numbers
4. Matter flows through “food cycle”
2. Trophic dynamics
The animal ecologists
1. Groundwork for thinking about energy
flow
2. But largely a “who’s there” approach
3. Biogeochemistry
Linsley pond, CT
G. Evelyn Hutchinson (1903-), Yale U.
1. Biogeochemical mode:
energy/material cycles are
influenced by the biota
2. Biodemographic mode:
mathematical studies of
variations in population size
3. Two modes conceptually linked by concept of selfregulation modes
4. Feedback cycles regulate coupling of biotic and abiotic
processes
3. Biogeochemistry
Linsley pond, CT
1. Biota influences chemical and physical
processes, which in turn affects biota
Plants
Nutrient cycling
Emergence of the ecosystem
concept
Arthur Tansley (1871-1955), Journal of Ecology
1. Melded “Clementsian” and
“Gleasonian” perspective
2. Objected to holism and organismal
concept, but also objected to
reductionism
3. Proposed the ECOSYSTEM
as middle ground: a system
made up of partially
overlapping systems
Ray Lindeman (1915-1942), Yale U.
1. Energy flows, while materials cycle
2. Changes in energy and material over succession, not
just “who’s there”
3. Ecosystem as integrated physical and biological
system
4. Died before he published his dissertation
The Odums:
Eugene (1913-2002), UGA and Howard (1922-2002),
UFL
1. Introduced new ecosystem tools to
ecologists (bomb tracers)
2. Used electrical circuits, cybernetics,
thermodynamics to describe ecosystems
3. The “macroscope”: spp. do not matter
4. Embraced Clements's “ecosystem as
organism”, alienated evolutionary and
pop. ecologists with discussions of
strategies and determinism
Eugene
Howard
Hans Jenny, U.C.-Berkeley (1899-1992):
State Factors
Climate
Time
Ecosystem
Soil and
structure
function
Relief
(Topography)
Organisms
Parent material
Ecosystem = (Cl, O, R, P, T)
State Factors
1. are independent of the system
being studied
2. control (in the ultimate sense)
the characteristics and properties
of ecosystems
Lecture ended here
The recent past:
1960s and ’70s:
International Biological Program
Hubbard Brook
Food webs and bioaccumulation
1980s:
1990s:
2000s:
Gaia
Non-equilibrium ecology
Long Term Ecological Research
Acid rain
Elevated CO2
Diversity and Ecosystem function
Hawai’i as a model system
BorEAS and LBA
The millenium report
The IPCC
Macro-ecology: scaling ind. to ecosystems
The nitrogen cycle
Where are we today?
• New tools—rapid analysis, isotopes,
models, global networks
Where are we today?
• Putting individualistic perspective within
context of overlapping systems
• Increasing awareness that organisms
cannot be “black-boxed”
• # and identity of species can affect
ecosystem processes
Where are we today?
• Understanding human-caused change
in the earth system
• Understanding feedbacks between
terrestrial ecosystems and global
climate
• Putting people into the picture…
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