Nature 408:79-82 (2000)

Elevated CO₂ increases productivity and invasive species success in an arid ecosystem

Stanley D. Smith*, Travis E. Huxman*†, Stephen F. Zitzer‡, Therese N. Charlet*, David C. Housman*, James S. Coleman§, Lynn K. Fenstermaker§, Jeffrey R. Seemann‡, and Robert S. Nowak‡

*Department of Biological Sciences, University of Nevada, Las Vegas, NV, 89154-4004, USA ;  ‡Department of Biochemistry, University of Nevada, Reno, NV, 89557, USA; § Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV, 89512 (J.S.C.) and Las Vegas, NV 89119 (L.K.F.), USA;   †Department of Environmental and Resource Sciences, University of Nevada, Reno, NV, 89557, USA

† Present address: Department of Environmental, Population, and Organismal Biology, University of Colorado, Boulder, CO, 80309, USA

*Corresponding author

Abstract

Arid ecosystems, which occupy about 20% of the earth’s terrestrial surface area, have been predicted to be one of the most responsive ecosystem types to elevated atmospheric CO₂ and associated global climate change. Utilizing Free-Air CO₂ Enrichment (FACE) technology in an intact Mojave Desert ecosystem, we found that the aboveground new shoot production of a dominant perennial shrub was doubled by a 50% increase in atmospheric CO₂ concentration in a high rainfall year. However, elevated CO₂ did not enhance production in a drought year. We also found that aboveground production and seed rain of an invasive annual grass increased at elevated CO₂ to a greater extent than in several species of native annuals. Consequently, elevated CO₂ could enhance the long-term success and dominance of exotic annual grasses in the region. This global change-driven shift in species composition in favor of exotic annual grasses has the potential to accelerate the fire cycle, reduce biodiversity, and alter ecosystem function in the deserts of western North America.