Post-wind vulnerability of boreal forests: Structural and site drivers of sequential snow and bark beetle disturbances

Understanding how an initial wind disturbance relates to subsequent forest damage is important for assessing forest resilience under climate change, yet it remains unclear whether wind mainly selects already vulnerable stands or is associated with stand conditions that shape later damage. We examined how stand structure, climate, topography, and species composition were associated with two common post-wind damage pathways in managed boreal forests across Finland: wind followed by bark beetle damage (WBB) and wind followed by snow damage (WS). Using Finnish Forest Use Declarations reporting damage and multi-source national forest inventory data, we fitted binomial generalised linear models for each pathway, a model contrasting the two pathways, and two baseline contrast models using damage records without prior wind as reference groups. Wind–bark beetle sequences were associated with higher basal area, greater structural heterogeneity, and southern locations, whereas wind–snow sequences were associated mainly with stand structure, topography, and the latitudinal gradient rather than with winter-climate variables. In contrast between the two post-wind pathways, growing degree days, lower elevation, and forest composition distinguished bark beetle outcomes from snow outcomes, with mixed stands showing a higher probability of a bark beetle outcome than pine-dominated stands. The baseline contrasts indicated that wind-initiated damage records differed in structural and site conditions from records of the same damage type without prior wind, suggesting that wind-initiated stands did not simply represent a random subset of later-damaged stands. The two post-wind pathways were therefore associated with different structural, climatic, topographic, and compositional conditions. These findings can support pathway-specific post-wind monitoring under increasing disturbance interactions.