Sturmschäden in ungleichförmigen Beständen | Storm damage in irregular stands

A selection forest covering about 500 ha in Schwarzenegg, on the southwest border of the Bernese Emmental, was subjected to areal and random spot checks in order to investigate dependencies between the damage caused by Lothar and various factors. Over the entire area 18% of the stems and 24% of the reserve stock is damaged. Worst hit are the acid and wet sites or low-lying sites. Selection sites are less effected than conversion stands and these less than even-aged stands. According to species, damage is significantly higher for spruce than for fir,and higher for fir than for beech. Yield intervention on sites up to 5 years before and between 15 and 20 years before the storm led to greater damage than intervention taken 5 to 15 years before the storm. Average strengths of interference between 70 to 150 sv/ha were less destabilising than weaker or stronger interference, regardless of how long before the storm they were carried out. It seems that, as far as risk reduction is concerned, selection forest is to be preferred to even-aged forest,as, in addition, permanent rejuvenation phases occur in selection stands over the whole area, which facilitate the reconstitution of structured stock in case of damage.