Spatially explicit forest management planning: Putting theory into practice

Background/Question/Methods

Forest ecosystems are facing novel conditions as the result of the synergistic interactions among natural disturbances (succession, fire, insect outbreaks, windthrow), anthropogenic direct activities (logging, land use change) and anthropogenic indirect activities (climate change). Ecological theory suggests that the spatial legacy past disturbances will affect the severity and extent of the subsequent disturbances in forested ecosystems. Ecological theory is difficult to extrapolate in the future given the long response times required to observe legacy effects in forested ecosystems and the stochasticity of large natural disturbances. Here we synthesize a body of research investigating interactions among logging patterns, fire disturbance, and spruce budworm outbreaks. A combination of published plot-scale studies, dendrochronology, remote sensing, and spatial analysis, are used to (1) define spatial legacies and disturbance regimes, and (2) parameterize landscape disturbance and succession models to investigate long-term interactions among logging, fire, and budworm disturbances. Empirical research was focused on a large landscape (Border Lake Landscape; BLL) where geopolitical boundaries have resulted in important land management legacies (managed forests in Minnesota, USA and in Ontario, Canada; and a large unmanaged wilderness). Simulation models were applied in parallel within the BLL and a comparable boreal mixedwood landscape in south-central Quebec.

Results/Conclusions

Patch analyses of land cover data for the BLL demonstrates a strong spatial legacy of logging on the size distribution of forest openings that was further reinforced by interactions between the differential disturbance regimes and the forest recovery process. The spatial legacy created by logging was tempered by the prominence of natural openings (i.e, lakes and wetlands) in the BLL, and current spatial structure of forest composition was only weakly related to land management zones. Reconstruction of budworm outbreaks suggests that logging legacies do influence outbreak dynamics (frequency, duration, spatial synchrony). Simulations suggest though that forest age structure and composition, not spatial pattern, underlies budworm – logging disturbance interactions. The different disturbance types have different consequences for both spatial and compositional legacies, and these differential legacies in turn influence future natural disturbances. Further, the cumulative effects of multiple disturbance types degrade these legacies over time. Such interacting processes illustrate the challenges of incorporating ecological theory into landscape-level planning. It is nonetheless clear that planning goals such as fire mitigation, ecosystem restoration, and sustainable forestry must account for the cumulative effects of interacting disturbances over long temporal and broad spatial scales within disturbance-prone systems such as the boreal mixedwood of North America.