Assessment of Tree Mortality After Windthrow using Photo-Derived Data

We used sequential surface photography and photo-derived data to evaluate tree mortality in a windthrow area in eastern Estonia, where a storm occurred in 2001. The study is based on photographs taken from the edge of three completely destroyed areas with total canopy destruction in which wind-felled spruce trees (Picea abies) were left after disturbance. In total, 137 spruce trees were observed over a five-year period. We used a transition matrix to examine tree mortality dynamics and patterns. At the end of the five-year period, only 25% of the spruce trees survived in areas surrounding the windthrow. The mortality was highest in the second year after disturbance and the probability of a tree falling was surprisingly high over the entire study period. According to local observations, Ips typographus caused most of the tree deaths, but the co-influences of other factors were also important as there was a large proportion of falling trees in the area.