Search

This article focuses on the ecological theory, which asserts that the climate of a region exerts top-down control on regional ecosystem patterns and processes, across space and time. Ecological processes may respond differently to climatic variation at each of these scales, depending on the region and ecosystem. Climate affects ecological processes both directly and indirectly, and complex-lagging patterns may exist. For example, interannual to decadal-scale changes in climatic regimes and ecosystem responses affect the demographic patterns of forests and meadows. Fire regimes in semiarid forests and woodlands in the southwestern U.S., in Colorado, and in Patagonia, Argentina, appear to be sensitive to climatic regimes characterized by interannual switching from wet to dry conditions on time scales of about two to four years. This wet/dry switching and low/high fire activity is often in phase with the ENSO and may be related to the importance of fine fuel for example growth, accumulation, and moisture content. In contrast, interannual switching from wet to dry is apparently less important in more productive pine forests of eastern Oregon than in the Southwest, but multiyear drought conditions may be more important to fire frequency patterns.