Boundary Dynamics: A Conceptual Framework for Studying Landscape Ecosystems

Abstract

We develop a conceptual foundation for the investigation of ecosystem patterns and processes that explicitly considers the spatial patchiness of ecological landscapes. Our emphasis is on the factors determining the location of boundaries between patch types in a landscape mosaic, how boundaries affect ecological processes and the movement of materials over an area, and how imbalances in these transfers in space can affect boundary characteristics and landscape configuration. We suggest that, other things being equal, the edaphic patterns of a landscape will determine the spatial patterning of the biota in the system, primarily through their effects on vegetation. Boundaries in a landscape may be located as direct consequences of the edaphic pattern, or may reflect perturbations of this underlying pattern due to physical disturbances or the actions of various transfer agents or vectors. Abiotic vectors such as wind or surface water flow respond differently to boundary features than do biotic vectors such as beetles or rodents. Both abiotic and biotic vectors may create disturbances through their actions, which in turn may alter patch boundary locations. Vectors also contribute directly to movements of materials, energy, or organisms over the landscape, both within and between patches, and thereby may determine the spatial patterns of the spread of perturbations through the system. If there are net imbalances in fluxes or the spread of disturbances across boundaries in relation to within-patch processes, a directional bias to system fluxes will be established. Over time, this changes the characteristics and locations of patch boundaries. Boundaries thus have dynamics that are superimposed on the edaphic foundation. Consideration of these dynamics offers the potential to gain insight into the spatial configuration of ecosystem functioning and emphasizes the value of a reductionist approach to ecosystem studies.