Consequences of More Extreme Precipitation Regimes for Terrestrial Ecosystems

H activities have caused dramatic and unprecedented changes in the global chemical and physical environment, including well-documented increases in atmospheric carbon dioxide (CO2) concentration and mean annual temperature (Karl and Knight 1998, New et al. 2001, IPCC 2007). If greenhouse gas emissions continue to increase at present rates, atmospheric CO2 concentrations will more than double preindustrial levels during the current century, and general circulation models (GCMs) predict additional increases in mean global temperature of between 1.1 and 6.4 degrees Celsius (IPCC 2007). Alterations in patterns of global atmospheric circulation and hydrologic processes are predicted to modify mean annual precipitation and to increase the interand intra-annual variability of precipitation (Easterling et al. 2000, Schär et al. 2004, Seneviratne et al. 2006, IPCC 2007). The combined effects of increased atmospheric CO2, elevated global temperatures, and altered precipitation regimes represent a rapid and unprecedented change to the fundamental drivers of chemical and biological processes within ecosystems (Amundson and Jenny 1997). The complexity and pace of these global anthropogenic changes pose a major challenge for ecosystem scientists and managers (NRC 2001), particularly given their potential impact on the provisioning of ecosystem services (Bennett et al. 2005). Amplification of the hydrological cycle, a consequence of global warming, has been expressed in the form of increased cloudiness, latent heat fluxes, and more frequent climate ex-