Coping with global environmental change through ecosystem-based management and restoration requires us to significantly improve our understanding of ecological succession. Central to ecology and ecosystem management, succession theory aims to explain and predict the assembly of ecological communities. Yet processes on lower hierarchical scales, for instance at the species and functional group level, are rarely linked to system-level indices that provide a deeper understanding of ecosystem processes and functioning and may be compared across ecosystems. The approach presented in chapter 1 combines established and new indices for quantifying successional progress from the functional group to the system level combining different bodies of theory to a comprehensive picture of successional progress in the pelagic zone of the large and deep Lake Constance. When moving from data analysis and interpretation to predicting the effects of changes in community composition on ecosystem structure, function, and services, it becomes critical to map ecological processes onto equations for modeling consumer-resource dynamics. Previously, the bottleneck of this endeavor had been other mechanistic models' inability to reproduce the dynamics of multiple populations interacting in the field. This limitation is overcome in chapter 2 by extending general consumer-resource network theory to the complex dynamics of the Lake Constance food web. Broadening the view beyond such isolated case studies allows the detection of (in)congruencies in the current theory of macroecological scaling and in the predicted effects of biodiversity (taxonomic and functional) on ecosystem functioning. In chapters 3-4, an integrated perspective across taxocenes (vascular plants, aquatic vertebrates, terrestrial invertebrates) and disparate habitats (deserts, forests, soil systems, seagrass meadows, rivers) under varying degrees of human influence is achieved.
In summary, this thesis helps to build a theoretical core for a synergy between ecosystem ecology and community ecology based on first principles. This encourages a scientifically optimistic outlook for the mechanistic understanding and the prediction of complex multi-species dynamics in natural ecosystems. In light of the approaches presented here, the goal of predicting biodiversity effects on ecosystem functioning and services by ecological modeling seems now more attainable than ever.
|Institution||University of Potsdam|