Dynamik der Wiederbewaldung im Waldbrandgebiet von Leuk (Wallis) | Recruitment dynamics following the forest fire near Leuk (Valais)

Abstract

After the intensive forest fire near Leuk, in 2003 the question arose whether and how fast the forest would regenerate. To answer this question, we observed the recolonisation by plants in the 300 ha of burned area annually from 2004 to 2008, using a set of permanently installed and systematically arranged sample plots of 200 m2 (n = 151). Five years after the fire, natural regeneration of the trees at altitudes above 1,700 m attains a density of 1,760 stems/ha, wich is comparable with results found after the forest fire in Val Müstair (Graubünden) in 1983, or after windthrow “Vivian” in 1990 in the Northern Prealps. The most frequent tree species are the pioneers, namely the European aspen (Populus tremula), large-leaved willow and goat willow (Salix appendiculata and S. caprea). Norway spruce (Picea abies) and European larch (Larix decidua) are present in small numbers. Natural regeneration is smaller at middle and lower altitudes, with roughly 1,160 stems/ha at altitudes between 1,300 and 1,700 m, and 700 stems/ha below 1,300 m. Here in many places pubescent oak (Quercus pubescens) regenerates itself with coppice shoots. Scots pine (Pinus sylvestris) regenerates only sparsely. By applying Ripley's K-function to triangle plots, we found that regeneration is significantly clumped in 79% of the plots having more than ten trees of at least 25 cm of height. Spatial aggregation often starts at very short distances between trees, and is observable both within and between species. Five years after the forest fire, we can confirm that forest will regenerate at all altitudes. The first forest phase will be bush forest.