Consequences of More Extreme Precipitation Regimes for Terrestrial Ecosystems

H uman activities have caused dramatic and un- precedented changes in the global chemical and physical environment, including well-documented increases in atmospheric carbon dioxide (CO 2 ) concentration and mean annual temperature If greenhouse gas emissions continue to increase at present rates, atmospheric CO 2 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 inter-and intra-annual variability of precipita-tion The combined effects of increased atmospheric CO 2 , 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