Streams and disturbance: are cross-ecosystem comparisons useful?
Disturbance is a pervasive influence in all ecosystems, but its effects vary widely. This is true both when quite different ecosystems are compared and when a suite of similar ecosystems, such as streams, is considered. Comparative approaches to ecosystem studies can provide insight into a complex process such as disturbance, but the power to resolve mechanistic questions diminishes as variance among the ecosystems that are compared increases. As a result, the usefulness of the comparative approach in ecosystem studies will depend on the goals of the investigation. Broad principles of ecosystem science may be revealed by comparison of very different ecosystems, but an understanding of underlying mechanisms shaping ecosystem structure and functioning still requires detailed studies of one or a few similar ecosystems. This is especially true when the process of interest is itself complex. Thus, a process such as disturbance may be best studied by comparing similar systems, whereas principles governing simpler attributes, such as decomposition rate or nutrient ratios, may be better elucidated by examining a wide range of ecosystem types.