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GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 17, NO. 2, 1067, doi:10.1029/2002GB001974, 2003

Vegetation sensitivity to global anthropogenic carbon dioxide emissions in a topographically complex region

Noah S. Diffenbaugh

Department of Earth Sciences, University of California, Santa Cruz, Santa Cruz, California, USA


Lisa C. Sloan

Department of Earth Sciences, University of California, Santa Cruz, Santa Cruz, California, USA


Mark A. Snyder

Department of Earth Sciences, University of California, Santa Cruz, Santa Cruz, California, USA


Jason L. Bell

Department of Earth Sciences, University of California, Santa Cruz, Santa Cruz, California, USA


Jed Kaplan

Max Planck Institute for Biogeochemistry, Jena, Germany


Sarah L. Shafer

U.S. Geological Survey, Corvallis, Oregon, USA


Patrick J. Bartlein

Department of Geography, University of Oregon, Eugene, Oregon, USA


Abstract

Anthropogenic increases in atmospheric carbon dioxide (CO2) concentrations may affect vegetation distribution both directly through changes in photosynthesis and water-use efficiency, and indirectly through CO2-induced climate change. Using an equilibrium vegetation model (BIOME4) driven by a regional climate model (RegCM2.5), we tested the sensitivity of vegetation in the western United States, a topographically complex region, to the direct, indirect, and combined effects of doubled preindustrial atmospheric CO2 concentrations. Those sensitivities were quantified using the kappa statistic. Simulated vegetation in the western United States was sensitive to changes in atmospheric CO2 concentrations, with woody biome types replacing less woody types throughout the domain. The simulated vegetation was also sensitive to climatic effects, particularly at high elevations, due to both warming throughout the domain and decreased precipitation in key mountain regions such as the Sierra Nevada of California and the Cascade and Blue Mountains of Oregon. Significantly, when the direct effects of CO2 on vegetation were tested in combination with the indirect effects of CO2-induced climate change, new vegetation patterns were created that were not seen in either of the individual cases. This result indicates that climatic and nonclimatic effects must be considered in tandem when assessing the potential impacts of elevated CO2 levels.

Received 21 August 2002; accepted 2 April 2003; published 12 June 2003.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1615 Global Change: Biogeochemical processes (4805); 1620 Global Change: Climate dynamics (3309); 6334 Policy Sciences: Regional planning.

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Citation: Diffenbaugh, N. S., L. C. Sloan, M. A. Snyder, J. L. Bell, J. Kaplan, S. L. Shafer, and P. J. Bartlein (2003), Vegetation sensitivity to global anthropogenic carbon dioxide emissions in a topographically complex region, Global Biogeochem. Cycles, 17(2), 1067, doi:10.1029/2002GB001974.