Langzeitforschung auf Sturmflächen zeigt Potenzial und Grenzen der Naturverjüngung

Abstract

Long-term research on storm areas demonstrates the potential and the limits of natural regeneration After windthrow, questions arise about the appropriate silvicultural management. Answers can be derived from long-term studies on 19 storm-damaged areas caused by Vivian (1990) and Lothar (1999), which encompass cleared, cleared and planted as well as uncleared subareas. Forest succession on these areas was studied using repeated regeneration inventories. Ten resp. 20 years after the storms, the resulting young forests were 3–12 m tall and had a stem density of 500 to 31,400 per ha. Many tree species grow in the storm areas, with climax species like European beech (in the lowlands) and Norway spruce (in high-altitude forests) being most frequent. Advance regeneration has only a small share of the young stands, since seedlings were scarce in the pre-storm stands. Regeneration is slightly more dense on cleared than on uncleared storm areas. The yearly increase in seedling density ranged from 25 to 4,000 trees per ha, with low values occurring mainly if dense vegetation of tall forbs, bramble or bracken covered the ground. The increase in density has fallen since the storms, and in thickets with high stem numbers, the regeneration density has even started to decrease. Pionieer trees as well as sycamore maple and ash grow fastest, and climax species like Norway spruce and silver fir slowest. For spruce, planting results in an advance of 1.0 to 2.4 m after 20 years in high montane storm areas; moreover, gaps, which are widespread in storm areas even 10 or 20 years after the storm event, can be avoided. On areas with total damage, cluster planting should be considered, in particular in protection forests and in cases with scarce advance regeneration, missing seed trees and dense ground vegetation.