Simulating the Effects of Alternative Forest Management Strategies on Landscape Structure

摘要

Quantitative, spatial tools are needed to assess the long-term spatial consequences of alternative management strategies for land use planning and resource management. We constructed a timber harvest allocation model (HARVEST) that provides a visual and quantitative means to predict the spatial pattern of forest openings produced by alternative harvest strategies. HARVEST was used to investigate the effect on landscape structure of alternate management plans formulated for the Hoosier National Forest (HNF) in southern Indiana, U.S.A. The 1985 Forest Plan for the HNF specified primarily clearcutting across most of the forest, and the 1991 Amended Forest Plan specified primarily group selection (removal of small groups of trees), limited to a much smaller portion of the forest. We assessed the relative importance of variation in the extent and intensity of timber harvest on landscape spatial pattern. We simulated 150 years for each alternative and calculated several measures of forest spatial pattern. The total area of forest interior and the mean size of forest interior blocks declined more under the 1985 Plan than under the 1991 Plan, primarily because of the greater area dedicated to timber production in the 1985 Plan. Despite the 65% decrease in timber production in the 1991 Plan, that Plan produced almost as much forest edge as the 1985 Plan due to heavy reliance on small harvests with large perimeter-to-area ratios. Both Plans resulted in an even distribution of age classes up to the age equal to rotation length, a dramatic decline in mid-age classes, and a large area of mature forest. The restriction of harvest activity to more limited areas in the 1991 Plan appeared to have a greater effect on forest spatial pattern than did the differences in harvest intensity of the two Plans. HARVEST provides a tool to link planning alternatives with potential changes in landscape structure, commodity production, and other resource values that are spatially dependent.