Evolution de la gestion des chablis ces 50 dernières années dans la région du Bas-Valais (essai)

Abstract

A review on the measures taken in forests hit by storms during the last 50 years reveals the mind-set behind the evolution of management operations. In the 1960s, to remove all dead wood in a stand was perfectly normal due to timber prices. Between 1984 and 1990, vast sums of money were pumped into the improvement of forest structures facing the threat of a general forest dieback. As a consequence, only few of the windthrow areas caused by storm Vivian remained with no intervention. Vivian also marked the beginning of manifold research activities and practical terrain examination in windthrow gaps. Conclusions of this first research phase resulted in a critical assessment of the windthrow areas caused by Lothar in 1999, considering different goals than systematic removal of damage wood and the prevention of bark beetle outbreaks. Since the 1990s, retaining timber after windthrow has been lively discussed, as well as the maintenance of the protection function against natural hazards and opportunities for biodiversity. Several handbooks were developed and successfully used for the planning and defining of top priority measures in damaged forests that resulted from disturbances in 2011 and 2012 in Lower Valais. These recent disturbances together with the certainty that storms will recur led to the formation of a task force in the canton Valais, aiming to organize both logistics and funds, as well as to define management priorities regarding a next hazard.