Does forest management abandonment matter more than habitat characteristics for ground beetles?

Abstract

Unmanaged forest reserves are designed to preserve or restore typical forest biodiversity, such as forest specialist or dispersal-limited forest species. Yet some species groups might be more dependent on specific habitat features than on forest management per se. We therefore investigated the respective influence of forest management abandonment and habitat characteristics on ground beetles in six French forests comprising both managed and unmanaged areas (85 plots). We hypothesised contrasted responses of carabid species richness depending on ecological and life-history traits (habitat affinity, dispersal ability, diet and moisture affinity). Management abandonment favoured only two ecological groups: forest specialists and openland species. For the other groups, management abandonment was not the main driver. Basal area and humus activity – respectively proxies for canopy closure and food supply – increased total species richness and richness of four ecological groups (forest, wingless, moisture indifferent and carnivorous species). Small scale variables, such as ground vegetation structure, most influenced habitat generalists, winged, hygrophilous and xerophilous species. The effect of forest management abandonment may have been limited either because the reserves we studied have been set aside too recently (15–45years ago), or because harvesting in the managed forests was relatively extensive (no clearcutting or slash harvesting). We emphasise the importance of taking stand structure into account to plan for biodiversity conservation in managed forests.