SYMP 13

High-Elevation Ecosystems in a Warmer World: Mechanisms of Change and Interactions Between Abiotic and Biotic Processes

Alpine and subalpine ecosystems are globally recognized as being highly vulnerable to climatic shifts. Warming temperatures and shifts in precipitation are expected to bring about extensive and possibly rapid changes to the structure, function, and composition of these high-elevation systems. These changes include an overall reduction in their area, large-scale alterations of physical processes, shifts in vegetation community boundaries, phenological shifts, and changes in composition of plant and animal communities. Moreover, because species are often unique, specialized, poor dispersers, and restricted in range, there are concerns that many will be unable to accommodate or adapt to new climatic regimes. Thus, many species may become more restricted in range and some could experience local extirpations. Evidence abounds that changes in high-elevation systems have been and are continuing to occur. However, there are also many indications, from both paleontological and contemporary data, that climate shifts will not necessarily have uniform effects on alpine and subalpine biota. Species responses can be very heterogeneous, with range shifts occurring in some regions and species but not others, or changes in abundance being driven by interactions among several biotic and abiotic processes. Moreover, although few disagree that alpine and subalpine ecosystems will continue to change, these changes may not necessarily be driven directly or exclusively by climate. Rather, they may occur through various pathways as a result of indirect effects from multiple factors interacting with climate and lead to a patchwork of alternative states. The key challenges then do not revolve around the question of whether change is happening; it is indeed already occurring. Instead, questions need to focus on sources of variability that could modify the rate, magnitude, and direction of change at different scales and levels of biological organization. The goal of this symposium is to focus on interactions between abiotic and biotic processes in high-elevation ecosystems. The talks will focus on: (1) mechanisms of change; and, (2) relationships among animal communities, vegetation communities, and climate. By focusing on mechanisms, we will advance perspectives beyond what might happen, to the reasons why and how animals are being affected by climate, how these relate to adaptations to changes in climate and their habitat, and to how plant-animal interactions such as herbivory and granivory could alter what are assumed to be inevitable changes in high-elevation vegetation communities.