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A General Model for Scaling Temperature and Biochemical Kinetics from Cells to Ecosystems.
Enquist, Brian*,1, 2, Economo, Evan1, Huxman, Travis1, Allen, Andrew3, Ignace, Danielle1, Gillooly, James3, 1 Department of Ecology and Evolutionary Biology, Tucson, AZ, USA2 Center for Applied Biodiversity Science, Washington, D.C., USA3 Department of Biology, Albuquerque, NM, USA
ABSTRACT- Understanding energy and material fluxes through ecosystems is central to many questions in global change biology and ecology. Our ability to predict variation in ecosystem processes is currently limited by our ability to mechanistically link biological processes across both spatial and temporal scales. One promising approach is to focus on how biotic and abiotic factors regulate metabolic rates of individuals, which combine to determine ecosystem flux rates. Metabolism is the fundamental process dictating material and energy fluxes through organisms. Here we derive a general biophysical model of ecosystem respiration based on the kinetics of metabolic reactions and the scaling of resource use by individual organisms. The model predicts that CO2 and energy flux is not constrained by ecosystem biomass, but is strongly influenced by temperature, variation in cellular metabolism, and rates of supply of limiting resources (water and / or nutrients). Analysis of intra-site variation in ecosystem respiration, as calculated using a global network of CO2 flux towers, provides robust support for the models predictions. However, data indicate that inter-site variation in annual flux is not strongly dependent on average site temperature or latitude. This presents an interesting paradox with respect to the expected temperature dependency. Nevertheless, our model provides a framework by which to quantitatively assess and integrate such additional biotic and abiotic influences on CO2 flux. Thus, a focus on the fundamental importance of metabolism offers a basis by which to integrate cellular, physiological and physical/ecological attributes of ecological systems.
Key words: Allometry, CO2 flux towers, Scaling, Ecosystem