Habitat patterns in forested landscapes: management practices and the uncertainty associated with natural disturbances

Abstract

We present the results of a study to examine the effects of management actions and natural disturbances in influencing the evolution of habitat patterns on forested lands. TELSA, a spatially explicit vegetation succession model with the ability to apply user-defined management actions and stochastic wildfires calibrated to local conditions, was used to evaluate changes in several indicators of habitat condition. We assessed seral stage and patch size changes over multiple 200-year simulations under a constant rate of harvest within each of these analyses. In the absence of natural disturbances, old growth habitat and large patches of forest of similar age and tree species composition decreased unless special management practices were applied. Old-growth management area reserves and periodic ‘aggregated cutblock’ harvesting entries helped maintain forest seral stage distribution at the target level, and patch size characteristics similar to the patterns that would have occurred under historic natural disturbances. Adding wildfire to the management scenarios substantially reduced the amount of old-growth habitat in designated old-growth management area reserves, compromising the ability to maintain old-growth at target levels. A 50% increase in the area designated as old-growth management area reserves would be required to offset the loss of old growth due to wildfire. Although the amount of old-growth habitat was diminished by wildfire, the availability of large habitat patches greater than 250 ha increased. We discuss the need to consider the role of management and natural disturbances in landscape planning, and suggest that redundancy is essential to maintain those features vulnerable to stochastic disturbances. Landscape scenario modeling can facilitate the development of risk averse plans, and encourage the development of innovative approaches to achieving timber and non-timber objectives.