Multifunctional management of mountain forests - Compromises between the protection and conservation functions

Abstract

Mountain forests are multifunctional forests that play a key role in both biodiversity conservation and rockfall protection. Most of these forests are in the process of secondary succession, where several stages with well differentiated diametric structures can be distinguished. These diametric structures strongly influence the two functions, i.e. biodiversity conservation and rockfall protection. The advanced stages of succession, representing mature forest, are the most important stages for conservation. The first, the ageing stage where the stand is still dominated by the initial cohort, has numerous, very large dominant trees. The two following stages, the renewal and irregular stages, are very heterogeneous in terms of tree dimensions. The most effective stages for rockfall protection are the densest stages, i.e. the first stage of the succession, the initial stage, and the irregular stage. In certain mountain-forest contexts, the irregular stage which optimises the two functions is difficult for forest managers to maintain. Consequently, when the protection function is the priority, it is recommended to precipitate the renewal of the stands by creating openings large enough to launch a new succession (from 0.1 to 0.5 ha). Forest management then organises the spatial and temporal distribution of these openings on a forested slope and aims to create a perennial mosaic of small groups of trees at initial, intermediate (self-thinning) and ageing stages. The latest stages of the succession, the best in terms of biodiversity, are often under-represented in this forest mosaic. The installation of small islands of carefully located old-growth stands makes it possible to compensate for this under-representation.