Evaluating the Relative Strengths of Biotic Versus Abiotic Controls on Ecosystem Processes
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There is no doubt that the rates of ecosystem processes and the resulting properties and structure of ecosystems are influenced both by biotic factors, including species properties and interactions among multiple species, and by abiotic factors, such as climate, geology, and soils. The critical issue (and the focus of the debate about diversity and ecosystem function) is the relative contribution of each of these general factors to any particular ecosystem process, under any particular conditions, and at any particular scale. While much remains to be learnt from future experiments, we can nonetheless evaluate the relative effects of biotic and abiotic factors in the results of current experiments, where they presumably result from processes operating in much the same way they operate under natural conditions. The detection of both types of factors in diversity experiments provides some insights into why these experiments have been so controversial. We will first review the patterns in natural systems that seem to contradict many of the experimental results, and then examine some of the experiments in more detail, in order to distinguish between biotic and abiotic effects.