Storm disturbance in forest ecosystems in Estonia

Several storms have damaged Estonian forests in recent years. Individual tree properties such as diameter at breast height (dbh) and tree height affect the type of damage (stem breakage or uprooting) and influence the formation of postdisturbance forest structure. The aim of this study was to analyse how the risk of uprooting and stem breakage varied with respect to tree diameter, height, species and soil conditions. The data were collected from plots located in storm-damaged forests in eastern Estonia. The probability of uprooting increased with increasing diameter for Norway spruce, European aspen and birch. Black alders with large stem diameter usually suffered stem breakage. A high proportion of stem breakage also occurred among small Norway spruce in the understorey, probably damaged by falling canopy trees. Soil conditions influenced the ratio between uprooting and stem breakage of Norway spruce, the ratio being much higher on gley soils than on podzolic soils. The root plate size of Norway spruce was only slightly correlated with dbh, tree height and volume.