Effects of Species Traits and Biodiversity on Ecosystem Processes in Arctic Tundra

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The objective of the proposed research is to explore the effects of biodiversity in plant species and of plant growth forms on ecosystem cycling of C and N in arctic tundra. In addition, it will test whether functional groups of plants are an adequate approximation for detailed physiological information on all species in understanding vegetation controls over ecosystem processes and the response of ecosystems to perturbations. Effort will be focused on arctic tundra, a high priority ecosystem. An integrated program of modeling and experimentation is proposed. Experimentally, diversity in the tundra will be manipulated by removing different growth forms of tundra plants (which represent functional groups in the tundra), and all possible combinations of the species from two growth forms, and effects on ecosystem C and N cycling will be measured. Simulation models will be developed to compare the effects of growth of individual plant species on ecosystem-level resource supply and cycling with those of functional groups constructed by averaging the characteristics of the different species in the growth form. Plant growth for each of the major species and competitive interactions during growth will be modeled. Model predictions of the distribution and net productivity of species or functional groups, ecosystem net primary productivity, and nutrient cycling under current climatic conditions will be compared. Effects of removing or introducing species or functional groups from the models, and of perturbations caused by herbivory or variable climate will also be examined, and will be compared with experimental results of removing species and growth forms. This research is novel because it is the first experimental test of the effects of species and growth form diversity on ecosystem processes in the tundra, and it is the first attempt to model the impact of plant species and their competitive interactions on ecosystem processes in arctic tundra. This is critical to understanding the role of species and functional group diversity in ecosystem processes.