Lehren aus Vivian für den Gebirgswald – im Hinblick auf den nächsten Sturm

Abstract

Lessons from Vivian for mountain forests – regarding the next storm The winter storm “Vivian” in February 1990 took Swiss forestry by surprise due to its enormous extent. It gave cause for entirely new and challenging questions for scientists and practitioners. Twenty-four years after the storm, the Swiss mountain forest tending group assessed in the frame of two workshops forest succession and the evolution of the protective effect against natural hazards in several well-documented Vivian storm areas at elevations between 1,500 and 1,700 m a.s.l. in the cantons of St. Gallen and Grisons. The decision to salvage the damaged timber or to leave it in place depends primarily on how the risk of bark beetle infestations is assessed. Lying stems can transiently reduce the risk created by natural hazards and favor stand establishment, by reducing snow movements and by serving as nurse logs in the long term. On several areas among those studied, forest succession has progressed so far that the protective effect is nearly restored. However, in the majority of the areas, this is not yet the case even 24 years after the storm. The presence of regeneration in the pre-storm stand, so-called advance regeneration, considerably accelerates forest succession in a windthrow area. If advance regeneration is absent, planting can considerably fasten succession in comparison to natural regeneration, which establishes often slowly. In summary, it is concluded that on large windthrow areas at high elevation the potential of natural regeneration is limited and that a more varied combination of the different treatment options should be envisaged in the case of future windthrow events.