16-­‐01-­‐07 What is an “Ecosystem” 160107 2 Early Ecosystem Defini;on: •  “Though the organisms may claim our primary interest, … we cannot separate them from their special environment, with which they form one physical system. It is the [eco]systems so formed which, from the point of view of the ecologist, are the basic units of nature on the face of the earth.” –  Arthur Tansley, 1935. 160107 3 1 16-­‐01-­‐07 Global ecology Ecosystems ecology ? Community ecology Popula;on ecology Physiological ecology Hierarchical Organiza.on of Ecology 160107 4 Microbial ecology Defini;ons •  Ecosystem – A bio;c community and its abio;c environment. Can be at any scale (micro to global). •  The “ecosystem” concept emphasizes the flow of ma/er and energy between living and non-­‐
living components. 160107 5 2 16-­‐01-­‐07 Topics in Ecosystems Ecology: •  Flow of ma/er and energy through living systems –  Energy (sunlight, temperature, radia;on, carbon) –  Water (hydrology, evapotranspira;on) –  Mineral Nutrient Cycling (nitrogen, phosphorus, iron….) •  Ecosystem metabolism: •  Photosynthesis “Produc;vity” •  Respira;on •  Other trace gas exchanges (CH4, N2O) •  Collec;vely, we refer to these as “ecosystem processes” or measures of “ecosystem func7on” 160107 6 •  Key ecosytem terms: -­‐ Spheres (biosphere, atmosphere, lithosphere, hydrosphere…) –  Fluxes (flow or movement) –  Pools (amounts in compartments) pool flux pool Biogeochemical cycles – movement of mader (e.g. C, H, N, O, P, S, H2O) between Earth’s different components (compartments) – biosphere, atmosphere, lithosphere, hydrosphere, etc. Since many of these are nutrients, we also call biogeochemical cycles “nutrient cycles.” 160107 7 3 16-­‐01-­‐07 Food web – how a community ecologist might view the world 160107 A marine food web: Note the many inter-­‐specific interac;ons Fig. 17.2, Molles & Cahill 2008 8 Trophic levels (pyramid) – an ecosystems view •  Primary producers = photoautotrophs (first trophic level) •  Primary consumers = herbivores (2nd trophic level) •  Secondary consumers = carnivores, insect parasitoids (3rd trophic level) •  Ter;ary consumers = higher carnivores, insect hyperparasites (4th trophic level) •  etc. Note that, from an ecosystems perspec7ve, individual species are abstracted into “func7onal groups” based on their role within an ecosystem. Carnivores herbivores Detritovores, Parasites photoautotrophs 160107 9 4 16-­‐01-­‐07 Energy flow through a forest Fig. 19.22 Molles & Cahill (Gosz et al. 1978) 160107 10 Note the dominance by primary producers and microbes Ecosystems also have other “func;ons”-­‐ e.g. provision of goods & services 160107 Land Conversion to human use alters biodiversity, along with many ecosystem goods & services 11 Foley et al. 2005 5 16-­‐01-­‐07 Biological Carbon Sequestra;on A = Geological carbon capture & storage (CCS) B = Biological CCS through reduced ;llage (C), biofuels (D), afforesta;on (E), avoided deforesta;on (F), and biochar applica;on (G) 160107 Gamon et al. (2011) The Case for a Biospheric Carbon Network (BCN) 12 hdp://biosphericcarbonnetwork.org Rela;ng Community Ecology to Ecosystem Ecology 160107 13 6 16-­‐01-­‐07 Cedar Creek LTER (Minnesota) In 1993, David Tilman and his colleagues set up 168 prairie plots (9 m * 9 m) with species richness ranging from 1 to 16 at Cedar Creek (Midelbach, 2012). Prairie plots at Cedar Creek Ecosystem Science Reserve, Minnesota, US 160107 hdps://www.cbs.umn.edu/explore/departments/eeb/faculty-­‐
14 research/directory/g-­‐david-­‐;lman Rela;ng community composi;on to ecosystem func;on Func;onal groups based on physiological and morphological differences, which influences in resource requirements, seasonality of growth, and life history. (Tilman et al., 1997) 160107 15 7 16-­‐01-­‐07 Rela;ng community composi;on to resilience (stable produc;vity in the face of drought) Tilman et al., 1994 160107 16 Forest fragments con;nue to suffer losses of biodiversity and biomass Laurance et al. 1997 160107 17 8