Introduction

Abstract

The Intergovernmental Panel on Climate Change (IPCC) concluded that climate changed during the past century, that human activities influenced the changes, and that climate is expected to continue to change in the future (Watson et al. 2002). The different scenarios studied indicate that continued increases in greenhouse gas concentrations will result in temperature increases from 1.4°C to 5.8°C (Houghton et al. 2001). This warming is expected to modify the global hydrologic cycle, resulting in increased winter precipitation at high latitudes, to result in more hot days and fewer cold days, and to change the frequency of droughts and floods, depending on location (Houghton et al. 2001). These predicted changes raise concerns about terrestrial ecosystem productivity, biogeochemical cycling, and the availability of water resources (Kirschbaum and Fischlin 1996; Melillo et al. 1990). As a result, the IPCC Working Group II Third Assessment Report (McCarthy et al. 2001) requested further research on the response of ecosystems to multiple stresses (e.g., increased temperature and drought).