LANDSCAPE DISTURBANCE MODELS AND THE LONG-TERM DYNAMICS OF NATURAL AREAS

The management of natural areas in disturbance-prone landscapes poses many challenges for which spatially explicit models can provide useful guidance. We have incorporated disturbance processes into simple land scape models and applied the results to two management issues. First, alternative disturbance scenarios were simulated as a function of land scape pattern and the frequency, spread, and severity of disturbance. The model simulates disturbance on random landscapes and for various l evels of landscape connectivity on subsections of Yellowstone National Park. Simulation results suggest that when the habitat that is suscep tible to a disturbance is well connected, the probability of disturban ce spread is most important in controlling the amount of habitat distu rbed. A critical threshold of habitat connectivity was observed in ran dom landscapes, but the actual landscape maps did not exhibit this thr eshold effect for the particular frequency and spread values used here . For a given proportion of the landscape occupied by susceptible habi tat, the variability in the amount of habitat affected by simulated di sturbances was much greater in the real landscapes than in the random landscapes. This difference suggests a strong interaction between the spatial configuration of susceptible habitat and the point of initiati on of the disturbances. Second, the results of a model that incorporat es disturbance and recovery dynamics suggest that qualitative shifts i n landscape behavior (e.g., from steady state to nonequilibrium) may o ccur, with important implications for natural area management.