Saproxylic beetle in logging residues: effects of tree species, diameter, decay stage

International audience; Converting fossil-based energy systems into carbon-neutral systems is an essential strategy to reach targets set by the Kyoto Protocol. For nations with a forestry industry, bioenergy based on logging residues or slash harvesting has a huge potential for development. However, forest fuel harvesting may have ecological consequences, notably for saproxylic biodiversity. Indeed, it reduces the volume of deadwood and is likely to alter the deadwood profile. However the consequences of such harvesting on biotic assemblages in temperate forests remains poorly documented. We compared the species richness and composition of saproxylic beetle assemblages among different types of logging residues. We asked if logging residues have a beetle fauna of conservation interest. Samples of logging residues were collected in 60 cutting areas, located in 12 forests from northern and south-eastern France. Our sampling design crossed four main factors describing deadwood type or environmental conditions: tree species (Quercus sp, Fagus sp, Carpinus sp, Picea abies), diameter class (5cm, 10 cm), age class (1 year after logging, more than 5 years after logging) and stand conditions. Four felling types were studied: young improvement cutting, mature improvement cutting, regeneration cut and coppice cutting. On the basis of previous boreal results, we hypothesized that tree species and diameter are the most important variables structuring saproxylic biodiversity. Our results will lead us to discuss the role of slash retention in maintaining the saproxylic biodiversity in temperate forests.