Modeling the effects of fire management alternatives on Sierra Nevada mixed-conifer forests

Decades of fire exclusion have led to hazardous fuel accumulations and the deterioration of fire-dependent ecosystems, particularly in the American We st. Managers are striving to return the ecological role of fire to many eco systems and would benefit from a much better understanding of how forest st ructure and composition might change if fires were reintroduced. We used a forest gap model, developed for forests in the Sierra Nevada, California, U SA, that integrates climate, fire, and forest dynamics to investigate fores t response to changes in the fire regime. The model simulates a spatially h eterogeneous fuel bed that is responsive to changes in forest condition, ma king it well suited for examining alternative management approaches for res toring Sierra Nevada forests after a century of fire exclusion. Presuppress ion forest basal area, species composition, and spatial autocorrelation str ucture were restored quickly, if simulated disturbances that caused substan tial tree mortality were reintroduced. Simulations of harvest induced the h ighest levels of mortality and, thus, most effectively restored forest stru cture and composition. However, prescribed fires were just as effective in restoring forest structure and composition if they were sufficiently severe .