Mitigating midterm timber supply shortage using commercial thinning operations. A case study from British Columbia, Canada

Forests in the interior of British Columbia, Canada have seen a substantial change in age class structure caused by a mountain pine beetle outbreak that instigated high tree mortality, and consequently, large scale salvage operations. The current age class structure in affected regions implies a midterm timber supply shortage that has the potential to negatively impact the forest industry in affected timber supply areas in the near future. A spatially explicit landscape level forest model for Bulkley timber supply area (TSA), a typical TSA facing these challenges, was developed. Using landscape level planning software we modelled future timber supply as well as age class structure over a 250-year planning horizon for (a) current single entry forest management practices focusing mainly on clearcutting; and (b) alternative management scenarios using multi-entry (thinning) approaches. Alternative scenarios were designed to determine economically viable forest management alternatives while mitigating midterm timber supply shortage, and converting the forest structure in the region towards a more even age-class distribution. Implementing commercial thinnings in stands located within 300 m of existing roads showed the highest potential to successfully mitigate midterm timber supply shortage if entries were scheduled based on culmination of mean annual increment rather than on a fixed minimum harvestable volume. The use of thinnings shortened the overall duration of the midterm timber supply shortage, reaching sustainable harvest levels sooner than if conventional approaches were used, and higher overall timber volumes available for harvest. Alternative approaches to current forest management practices in BC prove to be promising and should be considered where possible.