Rooted in Risk : How thinning shapes storm outcomes innorthern conifer stands
2025
Hedberg, Ola
Windstorms are a major disturbance factor in boreal forests, resulting in major economic losses forforest owners, particularly in Sweden’s conifer-dominated production landscapes. This studyinvestigates how commercial thinning and stand structure influence wind damage risk. A fieldinventory of 60 plots (30 thinned, 30 unthinned) was conducted in managed forests in Sollefteåmunicipality, where each plot was assessed for storm damage, tree height, stem density, and treespecies composition. Results from generalized linear models revealed that thinned stands hadsignificantly fewer wind-damaged trees in absolute terms, but the proportion of damaged stems wassimilar between thinned and unthinned stands. Tree height and stem density were positively correlatedwith damage risk, while species composition—including deciduous admixture—had no statisticallysignificant effect, likely due to limited compositional variation in the dataset. These results suggestthat thinning may reduce total damage by lowering stand density but does not necessarily improve per-tree resistance to winds. The findings indicate that while thinning reduces the total number of wind-damaged trees, it does not lower the proportion of trees damaged. Therefore, forest managers aimingto reduce storm risk should prioritize early density control through wide spacing or heavy pre-commercial thinning, rather than relying solely on mid-rotation commercial thinnings. Incorporatingwind-firm species such as birch may also enhance long-term stand stability.
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