📊 The influence of forest road networks on the long term impacts of uneven-aged management

Uneven-aged forest management is currently seen by many forest ecologists as an extensive management approach offering interesting compromises between timber production and other important ecosystem services such as biodiversity conservation, carbon storage, and social acceptability. While the benefits of uneven-aged management have been reported at the stand-scale and on short time periods, uncertainties remain concerning the impacts of uneven-aged management on longer time and wider spatial scales. Of concern are the impact of forest roads, as uneven-aged management necessitate more permanent roads and an increased road usage in order to accommodate shorter harvest rotations. These could in turn increase permanent forest lost, fauna road mortality, carbon emissions and operational costs for the industry.

To explore this question, we compared the impact of uneven-aged management with that of even-aged management at large time and spatial scales. We created a road extension for the LANDIS-II landscape simulation model, whose goal is to simulate the construction of forest roads to reach harvesting areas in a dynamic and spatially explicit way. Road trajectories are computed by minimizing construction costs according to existing roads, elevation, topography, water bodies, and soil types. We developed 20 scenarios with different proportions of harvested areas managed with uneven-aged or even aged management methods, for a given harvest wood volume. The scenarios also differed in the level of aggregation of the harvested areas, and in the presence of a pre-existing forest roads. We tested these scenarios over a planning horizon of 300 years on a landscape of 5 million hectares in Mauricie, Canada, and measured several characteristics of the road network for each scenario.

Our results will further our understanding of the long-term impacts of management strategies in forested landscapes, and will also open new opportunities to explore the impact of forest roads around the world.