Large-scale damage caused by the European spruce bark beetle (SBB; Ips typographus L.) to Norway spruce (Picea abies (L.) H. Karst.) forests have increased in recent decades. This thesis evaluate how stand, landscape and climatic attributes contribute to SBB damage and its spatial distribution in Finland. Sub-study I analysed the differences between SBB-damaged and undamaged stands, and the contribution of landscape attributes to the formation of new SBB damage. Sub-study II examined the spatial patterns of SBB damage and the contribution of stand and landscape attributes to the formation of SBB damage hotspots. Sub-study III developed spatially explicit probability models of SBB damage, considering stand, landscape and climatic attributes. The studies covered the southern Finland (11.4 million ha with more than two million Norway spruce stands) and utilised forest-use notifications of salvage loggings during 2012–2022, and Norway spruce forest stock data (Sub-study II).
Chi-squared and Mann-Whitney U tests were used to analyse differences between SBB-damaged and undamaged stands. Generalised linear mixed effects models were used to analyse the contribution of landscape attributes to the formation of new SBB damage (Sub-study I) and SBB-damage hotspots (Sub-study II), as well as to predict the probability of stand-level SBB damage (Sub-study III). Local Moran’s I was used to identify hotspots.
Mature Norway spruce stands with higher age and mean diameter, and those near recent clear-cuts, wind and SBB damage were most susceptible to SBB damage (Sub-study I) and those near recent SBB damage were most prone to form hotspots (Sub-study II). The best predictors of SBB damage were proximity to clear-cuts, mean stand diameter, distance to previous SBB damage and the number of consecutive days above 25°C (Sub-study III). Based on these findings effective proactive risk management options are needed to tackle the increasing risk of SBB damage under climate change.