Expanding the scale of forest management: allocating timber harvests in time and space

Abstract

This study examined the effect of clustering timber harvest zones and of changing the land use categories of zones (dynamic zoning) over varying temporal and spatial scales. Focusing on the Hoosier National Forest (HNF) in Indiana, USA as a study area, I used a timber harvest allocation nodel to simulate four management altermatives. In the static zoning alternative, harvests were dispersed throughout the timber harvest land base (65% of HNF) for 15 decades. The three dynamic zoning alternatives varied in the degree to which harvests were clustered in time and space. Two levels of harvest intensity were simulated, and at each level of harvest intensity, the area harvested was held constant among all four zoning alternatives. The dynamic zoning strategies resulted in substantial increases in the amount of forest interior and reductions in the amount of forest edge across the landscape, as well as an increase in the average age of stands when harvested. The greatest reduction in fragmentation was produced by the alternative that most tightly clustered harvests in time and space (i.e. intensive harvesting of small blocks in a relatively short time). When harvest intensity was high, this alternative produced amounts of forest interior and edge comparable to those of the dispersed alternative with half the rate of harvest. The results suggest that the injection of dynamics in specifying disturbance regimes, and the clustering of disturbance in time and space, can be used to sustain larger blocks of mature forest than can static zoning. Dynamic zoning encourages explicit specification of the disturbance regimes that will be imposed across the land base over long periods of time.