Document: AMY-3-52-41
Species, functional groups, diversity and composition: What regulates ecosystem function and stability?
DOWNING, A.L.*
The University of Chicago, Chicago, IL 60637 1
Abstract:
Species ultimately control energy and material flow through ecosystems. Here I describe work in which I ask if simplified descriptions of species in food webs, including species diversity and composition, and functional group diversity and composition, can be used to predict ecosystem function and stability. I independently manipulated species diversity, species composition, functional group diversity, and functional group composition in semi-natural pond mesocosms. Functional groups included macrophytes, herbivores, and invertebrate predators. Each food web was crossed with control and pulsed acidification treatments to explore the effects of food web structure on ecosystem stability. Ecosystem responses included productivity, respiration, nutrients, and community biomass. All food web properties had significant effects on some aspect of ecosystem function, however species composition and functional group composition had particularly strong effects. Ecosystem stability, quantified as resistance and resilience, was also sensitive to the underlying food web structure. More diverse communities tended to have increased resilience of productivity and respiration. Breaking food webs down into individual species' contributions to overall ecosystem function revealed that many species have large effects while others have little effect on function. These results suggest that although all aspects of food web structure are important for ecosystem function, the composition of species within a community largely determines function. However diversity effects may still be important in determining the response of ecosystems to disturbance.
Keywords: species, functional groups, diversity, composition, ecosystem function, ecosystem stability
This abstract is being presented at: 8:15 AM in session:
Oral Session #56: Metapopulation Analysis.