Vegetative Succession after Volcanic Eruptions: Review, Patterns and Processes

Disturbance is a fundamental part of ecosystems but varies in scale, intensity, frequency and resulting influence on species. Large infrequent disturbances are extreme in two or more of those aspects and may have disproportionate influences on resulting communities. Humans are altering landscapes at an unprecedented rate and frequently want to manage resulting landscapes for ecosystem services and quick recovery. By studying the way ecosystems reassemble after naturally occurring large, infrequent disturbances we can gain insight into how to effectively manage anthropogenically altered landscapes. Volcanic eruptions provide an excellent opportunity to study ecosystem assembly processes after disturbance because they often involve several disturbances differing in scale and severity but not in timing, thereby providing excellent opportunities to infer differences in processes. This thesis focuses mostly on vegetative recovery after volcanic debris avalanches, volcanic landslides, but will also addresses recovery processes within areas devastated by lateral blasts, pyroclastic flows and lahars. In each chapter vegetative community assembly after disturbance is examined from a different scale, starting with a global review of the literature. Next is a comparison of different volcanic disturbances at Mount St. Helens after its 1980 eruption, and finally, drivers of vegetation change are examined in detail on the debris avalanche deposit at Mount St. Helens.