Spatial heterogeneity

Spatial heterogeneity refers to the non-uniform distribution of organisms, resources, and environmental conditions across space. It is not merely a backdrop against which ecological processes occur; it is an active driver of those processes. A heterogeneous landscape creates a mosaic of microhabitats, each with its own species assemblage, disturbance history, and competitive regime. The diversity of the whole is often greater than the sum of the parts because edge effects, boundary dynamics, and cross-patch dispersal add layers of complexity not present in any single patch.

Spatial heterogeneity is the geographic substrate of the intermediate disturbance hypothesis. A uniform disturbance regime produces a uniform landscape of similar-aged patches and low beta diversity. A heterogeneous disturbance regime — one in which fire intensity, flood depth, or windthrow severity varies across space — produces a mosaic of patches at different successional stages, each with its own community. The spatial variation in disturbance is as important as the temporal variation, yet it receives far less theoretical attention. The field of landscape ecology exists to correct this imbalance.