The damage caused by wind in middle-aged Scots pine stands on permanent thinning experimental plots

Abstract In July 2002, the very strong hurricane appeared in northern Poland, which caused destruction of forest cover of area more than 10,000 ha. The permanent thinning research plot in a 53-year-old pine stand located in Myszyniec forest district (150 km north of Warsaw) was lying on the edge of damaged area. The following treatments were tested on this plot: 1) control plot (without thinning); 2) schematic cut in 20-year-old stand, selective thinning to 40 years, then thinning from below; 3) schematic cut in 20-year-old stand, then selective thinning; 4) selective thinning in young stand (20–40 years), then thinning from below and 5) selective thinning all the time. A significant part of this plot was completely destroyed and in the other part of the plot, some trees survived. A small part of the plot resisted the wind attack. An analysis of the amount of destroyed trees (measured by basal area) showed no differences between particular silvicultural treatments. The level of damage differed between particular parts of the plot. Another plot located in Ostrów Mazowiecka forest district (100 km NE of Warsaw) with the same thinning treatments was touched by heavy wind in July 2011 when the stand was 62 years old. Unlike the hurricane of 2002, this storm did not destroy the experimental plot which was located outside the zone of heaviest calamity. Therefore, damage on this plot had point and group character. Although on particular measurement units, share of broken or fallen trees did not exceed 10% of total basal area, it can be observed that the lowest level of damage was noticed on plots with selective thinning in young age and thinning from below in older stand.