| Summary: | Ecosystem functions are components of an ecosystem that change over time. We rely on many of these functions, such as carbon or water cycling, for survival. For over twenty years, ecologists have been vigorously testing the effects of biodiversity loss on ecosystem functioning. These experiments have nearly all been done either in growth chambers or carefully cultivated field communities. As ecologists frequently acknowledge, it remains to be determined how accurately the results of these studies portray the effects of biodiversity on ecosystem functioning in nature. Ecosystem functioning research has also emphasized biodiversity as the key variable, while other community properties and processes have gone largely ignored. I studied carbon cycling in Arctic tundra plants by focusing on the ecophysiology of respiration rates rather than biodiversity. I also conducted a biodiversity and ecosystem functioning experiment using natural, unmanipulated communities. Finally, I used the data from both of these experiments to quantify intraspecific variation in functional traits, a crucial tool in studies of ecosystem functions. I found that respiration rates in the unique constant daylight environment in the Arctic are much higher than would be expected from studies in temperate environments. In the biodiversity and ecosystem functioning experiment, I was unable to find any measurable effect of biodiversity on biomass production, marking a stark contrast from previous results in controlled experiments. I also found extensive intraspecific variation in many common functional traits, highlighting the importance of including these measurements in similar studies. Ph.D.
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