| Species and their abiotic environment are linked through dynamic feedbacks, yet understanding how species influence ecosystem dynamics is challenging due to the complexity and scale of communities and ecosystems. Recently, ecologists have begun to systematically explore the role of species in ecosystems by decomposing the complexity of biological diversity into simpler components. To understand how and when species influence ecosystem dynamics, I used experimental pond mesocosms to explore the contributions of four components of biodiversity for ecosystem dynamics. The components of biodiversity included functional group richness, functional group composition, within-functional group species richness, and within-functional group species composition. Functional groups were defined as groups of species sharing traits relevant for a particular ecosystem process or property, and included macrophytes, periphyton grazers, and invertebrate predators. To explore the role of biodiversity for ecosystem functioning and the stability of ecosystem functioning in response to disturbance, I conducted aquatic mesocosm experiments in which I manipulated all four components of biodiversity in pond food webs. I subsequently imposed a pulse acidification event, and monitored the response of six ecosystem response variables over time. The ecosystem response variables included productivity, respiration, decomposition, phytoplankton biomass, periphyton biomass, and zooplankton biomass.; Results indicated that richness influenced productivity and the partitioning of biomass in ponds. Importantly, species composition sometimes had stronger and more dramatic effects than average effects of species richness on certain ecosystem responses. Functional group composition and diversity revealed very little effect on ecosystem functioning, indicating that species influenced ecosystems through both direct and indirect effects that may be difficult to predict based on the association of a species to a particular functional group. Individual species effects on ecosystems varied with functional group, trophic rank, biotic, and abiotic factors. Finally, despite the importance of species composition for determining some ecosystem responses, species richness but not species composition enhanced ecosystem resilience after a disturbance. These combined results suggest different components of diversity are important for unique aspects of ecosystem dynamics. |
