5 - Equilibrium versus non-equilibrium landscapes

Summary

Landscapes have a spatial domain that can be relatively large or small with respect to their disturbance regime. The ratio of typical disturbance size and landscape spatial extent characterizes the overall landscape behavior as well as the relative predictability of this behavior. Large-scale environmental change, human land-use changes, and natural or human-induced changes in the climate can all alter the spatial and temporal domain of the disturbance, and thus change the degree to which one can predict a landscape's dynamic behavior.

Conceptual considerations

When disturbances are sufficiently small or frequent, they are incorporated into the environment of the ecosystem; when they are sufficiently large and infrequent, they are catastrophic (Fig. 5.1A). There is an intermediate scale of extent and occurrence at which disturbance enforces a mosaic pattern to the ecological landscape. In this case, the landscape pattern is a mosaic of patches – each patch with an internal homogeneity of recent disturbance history different from the surrounding patches.

The mosaic landscape is a statistical assemblage of patches. As in any sampled system, when the number of such patches is small, the variability is relatively large with related increased unpredictability (Fig. 5.1B). If the number of patches making up a landscape is large, the landscape dynamics will become more predictable. Climate change and human land-use changes tend to increase the size and synchronization of disturbances and make landscape dynamics less predictable (Fig. 5.1B).