In managed European hemiboreal forests, windstorms have a notable ecological and socio-economic impact. In this study, stand properties affecting windstorm damage occurrence at the stand-level were assessed using a Generalized Linear Mixed model. After 2005 windstorm, 5959 stands dominated by birch ( spp.), Scots pine ( L.) and Norway spruce ( (L.) Karst.), with mean height > 10 m were inventoried. Windstorm damage was positively associated with spruce and pine-dominated stands, increasing mean height, fresh forest edges, decreasing time since the last thinning and stronger wind gusts. Tree species composition – mixed or monodominant – was not statistically significant in the model; while, the admixture of spruce in the canopy layer was positively associated with higher windstorm damage. Stands on peat soils were more damaged than stands on mineral soils. Birch stands were more damaged than pine stands. This information could be used in forest management planning, selection of silvicultural treatments to increase forest resilience to natural disturbances.Betula Pinus sylvestris Picea abies

Bark stripping caused by cervids can have a long-lasting negative effect on tree vitality. Such trees of low vitality might be more susceptible to other disturbances. The amplifying effects of disturbance interactions can cause significantly more damage to forest ecosystems than the individual effects of each disturbance. Therefore, this study aimed to assess the impact of bark stripping (stem damage) on the probability of wind damage and snapping height for Norway spruces (Picea Abies (L.) H. Karst.). In this study, we used the Latvian National Forest Inventory data from the period 2004–2018. In the analysis, we used data based on 32,856 trees. To analyse the data, we implemented a Bayesian binary logistic generalised linear mixed-effects model and the linear mixed-effects model. Our results showed that stem damage significantly increased the probability of wind damage and affected the snapping height of Norway spruces. Similarly, root damage, the slenderness ratio, the stand age, the stand density, the soil type, and the dominant tree species had a significant influence on the probability of wind damage. In both periods, trees with stem damage had significantly (p < 0.05) higher probability (odd ratio 1.68) to be wind damaged than trees without stem damage. The stem damaged Norway spruce trees snapped in the first 25% of the tree height, while trees without stem damage snapped around half (50%) of the tree height. Our results show that stem damage significantly alters the effect of wind damage on Norway spruces, suggesting that such damage must be incorporated into wind-risk assessment models.

Windstorms are a significant disturbance in northern European Scots pine forests. Mechanistic models for assessment of their impact have been developed. The aim of our study was to assess the impact of windstorms on the financial value of Scots pine (Pinus sylvestris L.) stands. Wind damage probability in stands with certain dimensions (linked to age and site index) and the reduced value retrieved from salvage logging instead of planned harvest in undamaged stands were used for calculation. Equivalent annual annuity with interest rates of 3%, 4%, and 5%, three different commercial thinning regimes, and different planting densities were used to assess the mean influence. Wind damage risk had a notable and significant negative effect on the financial value of Scots pine forest stands. Equivalent annual annuity decreased sharply with stand age, especially in the most productive sites (SI 36). The negative financial impact could be reduced by selection of a lower initial planting density (1000–2000 trees ha⁻¹ instead of 3000) and by reducing the rotation period, for example, by using target diameter as the criteria for the time of final harvest.

Norway spruce is a relatively fast-growing tree species that is primarily regenerated by planting, which requires significant investments. The formation of lammas shoots (i.e., second flushing in late summer) have been proven to affect the quality and productivity of Norway spruce stands. The aim of our study was to assess the proportion of trees with lammas shoots in young stands of Norway spruce and to investigate the factors affecting their formation. Data have been collected at the end of 2011 in 102 three- to seven-year-old Norway spruce plantations randomly selected across different forest types in the central part of Latvia, and a subset of 21 stands were inventoried again at the end of 2012. In each stand, 20 sample plots were systematically established where trees with and without lammas shoots were counted and micro-environmental factors (moisture, competition, and browsing) were assessed on a three-grade scale. On average, the proportion of trees with lammas shoots was 6.5%. There was no significant effect of the stand age (from 3 to 7 years) on the proportion of trees with lammas shoots nor was there any age-related trend. The effect of forest type on the presence of lammas shoots was not significant. Micro-environmental factors had an important influence on the proportion of trees with lammas shoots. The proportion of lammas shoots in stands with no competition was significantly higher (14.5%) compared to stands with medium and high competition (6.0% and 2.2%, respectively). Similarly, a significantly higher proportion of trees with lammas shoots (11.7%) was observed in sites with normal moisture regime than in sites with slight or notable excess moisture, reaching 4.8% and 1.7%, respectively. Although the influence of browsing damage was not statistically significant, its trend was similar to that observed for competition and moisture regime. Overall, the proportion of trees with lammas shoots was highest in stands showing the most suitable micro-environmental conditions for Norway spruce.