Impacts of Global Change on Composition of Arctic Communities: Implications for Ecosystem Functioning

Abstract

As a result of the increasing atmospheric concentrations of radiatively active greenhouse gases, global temperatures are expected to rise (Houghton et al., 1990), particularly at high latitudes. Current global temperature trends are consistent with these predictions (Maxwell, 1992). Accompanying this climatic warming will be changes in growing season length, irradiance, permafrost depth, soil moisture, and nutrient availability (Chapin et al., 1992; Kane et al., 1992; Maxwell, 1992), although the exact nature and magnitude of these changes are less certain than those of temperature change. Other, more direct, human impacts on arctic ecosystems may be even more important than climatic change in the next few decades, including air pollution, disturbance associated with resource exploitation, and altered grazing regime due to changing patterns of reindeer husbandry and hunting. Together these global changes in environment are certain to affect arctic communities. The challenge is to predict how community composition will respond to these environmental changes and what will be the consequences for arctic ecosystems. In this chapter we present a framework for predicting how arctic plant communities will respond to global change and discuss the implications for ecosystem functioning. Detailed justification for this approach is provided elsewhere in general terms (Chapin, 1993; Hobbie et al., 1993; Shaver et al., 1992) and for tundra (Chapin et al., 1995).