Waldverjüngung und Totholz in Sturmflächen 10 Jahre nach Lothar und 20 Jahre nach Vivian

Abstract

Tree regeneration in Swiss forests after winter storms Lothar (1999) and Vivian (1990) was analysed based on a sample of 90 totally wind damaged forest gaps of at least 3 ha size, located in the Jura Mountains, the Central plateau, the Prealps and parts of the Alps. In the less elevated Lothar gaps (∅ 860 m a.s.l.) mean stem densities in no intervention gaps (NI) were 7,644 and in salvage logged gaps (SL) 10,786. Means in Vivian gaps (∅ 1428 m a.s.l.) were significantly smaller with 2,572 in NI and 4,600 in SL gaps. Pre-storm regeneration in Lothar gaps amounted to one third of the total stem density and in Vivian gaps to one tenth. The ten tallest trees in both Lothar and Vivian gaps were similar sized with 6.3 m and 6.5 m in average. Most abundant tree species were beech (Fagus sylvatica), sycamore (Acer pseudoplatanus), ash (Fraxinus excelsior) and Norway spruce (Picea abies) in Lothar gaps, and Norway spruce, sycamore and rowan (Sorbus aucuparia) in Vivian gaps. Stem density increased with soil pH and decreased with elevation and the portion of tall herbs, raspberry and blackberry. The deadwood volume amounted to average 266 and 285 m3 per ha in NI gaps of Lothar and Vivian, respectively. In the SL gaps, volumes averaged to 74 and 76 m3 per ha, respectively. Deadwood as regeneration substrate matters predominantly in forests at higher elevations and favouring Norway spruce in particular. Natural regeneration takes place in all studied forest gaps, sooner or later. To achieve specific forest aims, however, competing understory vegetation needs to be controlled. Our results serve as a reference for tree regeneration in wind damaged forests of Central Europe.