Boundaries and corridors as a continuum of ecological flow control: Lessons from rivers and streams

Landscape boundaries and corridors are areas of small spatial extent relati ve to their large effects on ecological flows. The trend in ecological lite rature is to treat corridors and boundaries as separate phenomena on the la ndscape. This approach, however, misses a fundamental aspect they have in c ommon: their strong influence on ecological flows. Corridors and boundaries exist at opposite ends of a permeability gradient, differing in their effe cts on rates and direction of flow. The position of landscape structures al ong this permeability gradient depends on attributes of both the flow and o f the structure itself. We discuss boundaries and corridors in terms of mov er specificity, scale, and effects on different levels of ecological organi zation, using rivers and streams to illustrate our points. We predict which structures will act as boundaries or corridors and at what spatial and tem poral scales they are likely to be relevant. considering the function of la ndscape structures across the boundary-corridor continuum will provide rese archers and managers with a more complete, holistic viewpoint and will allo w better strategies to attain conservation goals.