ECOLOGICAL MECHANISMS AND LANDSCAPE ECOLOGY

Landscape ecology deals with the effects of the spatial configuration of mosaics on a wide variety of ecological phenomena. Because problems in many areas of conservation biology and resource management are related to landscape use, development of a rigorous theoretical and empirical foundation for landscape ecology is essential. We present an approach to research that focuses on how individual-level mechanisms operating in a heterogeneous mosaic produce ecological patterns that are spatially dependent. The theoretical framework that we develop considers the density and distribution of a population among patches as a function of (a) within-patch movement patterns of individuals; (b) emigration from patches as a function of population density, patch configuration, patch context, and within-patch movement; and (c) loss of individuals as they disperse through landscape elements. This theoretical framework is coupled with an empirical approach that emphasizes the use of experimental model systems (EMS), small-scale systems occupying ''microlandscapes.'' Such systems are amenable to experimental manipulation with adequate replication and control and may serve as analogs of systems occurring at broader landscape scales. where rigorous empirical work is more difficult. We illustrate the use of EMS with examples from our studies of beetles and ants in North America and of voles in Norway. Finally, we consider some factors that may constrain extrapolations from EMS to other systems, scales, or levels. We believe that implementation of a mechanistic approach to landscape ecology is essential to deriving generalizations about how spatial heterogeneity influences ecological systems.