Integrative forest management can promote biodiversity

Abstract

Integrative conservation strategies that combine production of commodities and conservation, are considered as a valuable tool to promote biodiversity in unprotected areas. In forests, a considerable proportion of biodiversity is dependent on deadwood structures, and an enrichment of deadwood is often proposed as important integrative conservation measure. The Bavarian State Forestry in Germany has implemented an integrative nature conservation strategy where the key element is the enrichment of deadwood during harvests. Deadwood is accumulated by leaving large and small diameter wood usually sold as firewood (discolored stems, crowns) after harvest combined with a retention of naturally developed deadwood. We examined the execution of this strategy in a forestry department in Bavaria (Germany), where it was implemented in 2006. We could show that with the implementation of the strategy deadwood amounts increased considerably. Therefore, we tested whether this strategy promotes biodiversity and influences assembly patterns of different species groups, which can give indications of a change in underlying mechanisms that shape the species communities, e.g. a change in the availability of niches. We conducted a before-after study to analyze the species numbers and the assembly pattern, based on functional-phylogenetic distance, of saproxylic beetles, saproxylic fungi, bird and plant assemblages in 68 beech forest plots. The plots were placed in forest nature reserves and production forest to include natural enrichment in reserves and active enrichment in production forests, which are both a part of the strategy. We tested whether integrative deadwood enrichment promotes the species numbers of the examined taxa and shifts the assembly pattern of the communities. For the assessment of assembly pattern, we used a distance matrix that combines functional and phylogenetic distance. With increasing deadwood amounts the species numbers of saproxylic beetles and fungi increased. The increases of species numbers occurred both in production forests with deadwood enrichment and in forest reserves. The species numbers of birds or plants did not change with deadwood enrichment. The functional-phylogenetic distance of saproxylic beetles increased towards an overdispersed pattern, i.e. increasing functional and phylogenetic dissimilarity between beetle species in the community, indicating an increase in the number of available niches with deadwood enrichment. Assembly patterns of the other examined taxa were unaffected by deadwood enrichment. This evaluation reveals a success of integrative deadwood enrichment in promoting the species numbers of saproxylic species and showing a fast increasing of niches for beetle communities.