Optimized harvest planning under alternative foliage-protection scenarios to reduce volume losses to spruce budworm

Abstract

Spruce budworm ( Choristoneura fumiferana Clem.) severely defoliates balsam fir ( Abies balsamea (L.) Mill.) and spruce ( Picea spp.) in large periodic outbreaks and represents one of Canada’s most damaging and widespread forest insects. We present a modeling framework that integrates stand-level spruce budworm volume impacts used in the Spruce Budworm Decision Support System (SBWDSS) into an industrial-scale timber supply model for the 209 000 ha Black Brook District in northwestern New Brunswick, Canada. This approach uses linear optimization of harvest scheduling, salvage, and insecticide application to minimize volume reduction. One hundred and ninety-five scenarios were simulated, including normal and severe spruce budworm outbreaks, beginning in 2002, with combinations of varying insecticide efficacy, timing, and spatial extent of protection. After simulated severe defoliation from 2007 to 2016, maximum harvest reductions of 35% were predicted for a normal outbreak for the 2012–2016 period, and 46% for a severe outbreak for the 2017–2021 period; these impacts were reduced to 25% and 34% using re-optimized harvest scheduling and salvage. Results suggest that combined optimized salvage and harvest rescheduling could reduce future harvest reductions by up to 12%. Spatial optimization of protected areas gave similar results to those obtained using protection priority assignments based on marginal stand-level volume reduction in the SBWDSS.