Why Link Species and Ecosystems? A Perspective from Ecosystem Ecology

Summary

Population, community, and ecosystem ecologists historically have asked different kinds of questions about nature, and as a result have defined domains of study quite differently. In this chapter, the general question “Why link species and ecosystems?” will be explored from an ecosystem ecologist’s point of view. I begin by considering the subdisciplinary distinctions in ecology: how they are reflected in questions asked, what theories underlie them, and what areas are ripe for integration.

Examples drawn largely from stream ecology are presented in a discussion of redundancy and keystone species. The primary conclusion is that these phenomena occur in nature, are applicable to ecosystem processes as well as community structure, and should be predictable from ecosystem and species characteristics. Although available data do not always allow prediction of which species is likely to affect ecosystem functioning, use of variables such as biomass or production as indicators of a given species’ status may lead to misinterpretation. Concepts of interaction strength are applicable to ecosystem studies.

Species occur in nature as members of interactive assemblages, and their interactions may affect ecosystem functioning in either subtle or dramatic ways. Given the attention that has been paid by community ecologists to biotic interactions, does an understanding of these processes contribute to understanding ecosystem functioning? A complex stream system and conceptual model are described for the purpose of highlighting questions relevant to integrating biotic interactions, disturbance, and ecosystem functioning.

Finally, some loose ideas on the themes of disturbance and stability, patchiness, and scale as potential starting points for linking species and ecosystems are given in the final section. To facilitate interaction between population/community and ecosystem/landscape ecology, units of study should be spatially based.