Approximating natural landscape pattern using aggregated harvest

Abstract

Successful implementation of the natural disturbance model for timber harvest is hindered by the lack of strategies to approximate landscape fire pattern. In the forests of Alberta, Canada, the fire regime is dominated by large fires that create large regions of same-aged forest. Current forestry practices disperse harvest blocks across the landscape, causing increased fragmentation as compared with fire. Aggregating harvest blocks is one potential strategy to improve approximation of natural landscape pattern. We used a simulation approach to compare landscape pattern created by aggregated harvest strategies, the current dispersed harvest approach, and the natural disturbance regime for a 270 000 ha forest landscape in northeastern Alberta. Compared with dispersed harvest, aggregated strategies increased compatibility with natural landscape pattern by reducing fragmentation. Capacity to aggregate harvest declined when the constraint of maintaining a constant proportion of deciduous to coniferous harvest was included. We conclude that aggregated harvest can improve implementation of the natural disturbance model by bringing several landscape metrics closer to the conditions that fall within the natural range of variability. Aggregated harvest alone, however, performed poorly at maintaining interior old forest, emphasizing that an explicit old-forest strategy is also required.