Evaluation of commercial thinning prescriptions based on stand density measures in hardwood-dominated stands in New Brunswick

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University of New Brunswick
This study focused on analysing effects of thinning prescriptions for tolerant hardwood sawlog production, more specifically on sugar maple (Acer saccharum) and yellow birch (Betulla aleghaniensis). Prescriptions tested considered a range of thinning intensities and timings based on a stand Relative Density (RD) measure. The main attributes analysed were gross merchantable volume, sawlog production, and sugar maple and yellow birch sawlog content. The Open Stand Model (OSM), a tree list growth simulation model, was used to simulate and project growth of hardwood-dominated plots. In total, 40 plots were selected from the permanent sample plots dataset (PSP) – Plot Co-op data from the Department of Energy Resource and Resource Development (ERD) of New Brunswick. Only the first measurement for each plot was considered, and the selection criteria were based on high-value species content and development stage. The best scenario in terms of total gross merchantable volume, sawlog volume production and yellow birch and sugar maple sawlog content was thinning stands when they reached 80% of RD and reducing RD to 60%. This option was the lightest thinning simulated. Average gain in volume of sugar maple and yellow birch was 8% across all plots.