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We modeled the integrated effects of natural disturbances and management activities for three disturbance scenarios on a 178,000 ha landscape in the upper Grande Ronde Subbasin of northeast Oregon. The landscape included three forest environments (warm-dry, cool-moist, and cold) as well as a mixture of publicly and privately owned lands. Our models were state and transition formulations that treat vegetation change as probabilistic transitions among structure and cover types. We simulated background natural disturbance (i.e., historical), active fuel treatment, and fire suppression only disturbance scenarios for 200 or 500 years, depending on scenario. Several interesting landscape hypotheses emerge from our scenario simulations: (1) changes in management approach in landscapes the size of our study area may take decades to play out owing to the time required to grow large trees and the feedback loops among disturbances, (2) the current landscape is considerably different from that which might exist under a natural disturbance regime, (3) fire suppression alone does not mimic background natural disturbances and does not produce abundant large tree structure, and (4) dense, multi-layered large tree forests may be particularly difficult to maintain in abundance in this and similar landscapes owing to wildfire and insect disturbances.
