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Ecosystem Ecology
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Ecosystem Ecology

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  1. Ecosystem Ecology Study of interactions among organisms and their physical environment as an integrated system

  2. What is an ecosystem? bounded ecological system consisting of all the organisms in an area and the physical environment with which they interact

  3. The ecosystem concept Biogeochemistry Ecological succession Trophic dynamics

  4. 1. Ecological succession The Midwestern botanists

  5. Henry Cowles (1869-1939), U. of Chicago • Vegetation changes in time in response to stress • Orderly development against backdrop of unpredictable physical disturbance • Plant communities are dynamic; ever-changing…

  6. Frederic Clements (1874-1945), U of MN and Carnegie Institute • Succession is a predictable linear process to a climax community • Community is analogous to an organism; the “superorganism”

  7. Henry Gleason (1882-1975), U of MI and NY Botanical Garden • Individualistic concept of plant communities • Communities are an assemblage of organisms, not an “organismal entity” • Major critic of Clements • Bryologist!

  8. 1. Ecological succession The Midwestern botanists • Plant communities are dynamic • Communities are analogous to organisms -versus- • Communities are assemblages of individuals

  9. 2. Trophic dynamics The animal ecologists

  10. Charles Elton (1900-1981), Oxford U. and the Bureau of Animal Populations • Niche concept • Niches are linked into food chains • Pyramid of numbers • Matter flows through “food cycle”

  11. 2. Trophic dynamics The animal ecologists • Groundwork for thinking about energy flow • But largely a “who’s there” approach

  12. 3. Biogeochemistry Linsley pond, CT

  13. G. Evelyn Hutchinson (1903-), Yale U. • Biogeochemical mode: energy/material cycles are influenced by the biota • Biodemographic mode: mathematical studies of variations in population size 3. Two modes conceptually linked by concept of self-regulation modes 4. Feedback cycles regulate coupling of biotic and abiotic processes

  14. 3. Biogeochemistry Linsley pond, CT • Biota influences chemical and physical processes, which in turn affects biota Plants Nutrient cycling

  15. Emergence of the ecosystem concept

  16. Arthur Tansley (1871-1955), Journal of Ecology • Melded “Clementsian” and “Gleasonian” perspective • 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

  17. Ray Lindeman (1915-1942), Yale U. • Energy flows, while materials cycle • Changes in energy and material over succession, not just “who’s there” • Ecosystem as integrated physical and biological system • Died before he published his dissertation

  18. The Odums: Eugene (1913-2002), UGA and Howard (1922-2002), UFL • Introduced new ecosystem tools to ecologists (bomb tracers) • Used electrical circuits, cybernetics, thermodynamics to describe ecosystems • The “macroscope”: spp. do not matter • Embraced Clements's “ecosystem as organism”, alienated evolutionary and pop. ecologists with discussions of strategies and determinism Howard Eugene

  19. Hans Jenny, U.C.-Berkeley (1899-1992): State Factors Climate Time Ecosystem structure and function Soil Relief (Topography) Organisms Parent material Ecosystem = (Cl, O, R, P, T)

  20. State Factors 1. are independent of the system being studied 2. control (in the ultimate sense) the characteristics and properties of ecosystems

  21. Lecture ended here

  22. The recent past: 1960s and ’70s: International Biological Program Hubbard Brook Food webs and bioaccumulation 1980s: Gaia Non-equilibrium ecology Long Term Ecological Research Acid rain 1990s: Elevated CO2 Diversity and Ecosystem function Hawai’i as a model system BorEAS and LBA 2000s: The millenium report The IPCC Macro-ecology: scaling ind. to ecosystems The nitrogen cycle

  23. Where are we today? • New tools—rapid analysis, isotopes, models, global networks

  24. 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

  25. 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…