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Abstract. Ecology of the saproxylic beetles in mountain forests of the northern French Alps.Both saproxylic beetles and deadwood stocks were studied in order to detect special deadwood features important for these organisms, and to better understand their ecology. A total of 37 window traps were used in ten stations covering four mountain forests in the French northern Alps. In the same time, the deadwood stocks were inventoried in the ten stations. 181 m 3 of deadwood (1219 fragments) were measured and 4268 individuals belonging to 235 saproxylic species were trapped. The deadwood volume ranges from 21.1 to 233.6 m 3 /ha and the number of beetle species from 27 to 113. A positive relation was observed between the stand age, the whole volume of deadwood and the species richness of saproxylic beetles. However, in some deadwood rich sites the beetle diversity is not as high as expected. This was explained by the negative influence of the management history of the forest. The compositions of saproxylic communities depend also of some characteristics of the deadwood stocks. Xylophagous and zoophagous species prefer "not lying and recently dead softwood" while the mycophagous and saproxylophagous species are strongly dependent on fungi growing on hardwood, respectively under "large surfaces of barks" and in "large woody debris". Surprisingly, the majority of the saproxylic beetles living on softwood does not depend on the most represented resinous deadwood type: the "decayed and lying softwood". Résumé.Les coléoptères saproxyliques et les stocks de bois mort ont été étudiés conjointement dans le but de déterminer les caractères importants du bois mort vis-à-vis de ces espèces mais également de mieux connaître leur écologie. Un total de trente sept pièges vitre a été utilisé dans dix stations couvrant quatre forêts de l'étage montagnard des Alpes du nord françaises. 181 m 3 de bois mort (1219 fragments) ont été mesurés et 4268 individus appartenant à 235 espèces saproxyliques ont été piégés. Le volume de bois mort varie d'une station à l'autre depuis 21,1 jusqu'à 233,6 m 3 /ha. Le nombre d'espèces va quant à lui de 27 à 113 selon les pièges. Une relation positive a été observée entre l'âge de la station, le volume de bois mort et la richesse spécifique des coléoptères saproxyliques. Pourtant, dans certains sites, la diversité spécifique n'est pas aussi élevée qu'attendu. Ceci est expliqué par l'influence négative de l'histoire de la gestion de la forêt. Les compositions des communautés de coléoptères saproxyliques dépendent aussi des essences en présence dans les stocks de bois mort. Les xylophages et les zoophages préfèrent les « bois de résineux mort récemment et éloignés du sol » tandis que les mycophages et les saproxylophages sont fortement dépendants des champignons poussant sur les bois de feuillus et respectivement sous « les larges surfaces d'écorce » et dans les « grands fragments de bois mort ». Il est remarquable que la majorité des coléoptères saproxyliques vivant sur le bois mort de résineux ne dépende p...

This study compared the richness of saproxylic beetle species and the composition of species assemblages between the major forests types of the south-east of France. The forests differed by their geographical position and their composition in tree species. The results confirmed the existence of a clear local identity of the saproxylic beetles communities. This identity combined three geographical and ecological factors: the geographical position, the altitude and the dominant species of trees. Surprisingly, the period length since the last important perturbation of the stand was not a determinant factor to explain the composition of the saproxylic communities. Selective logging and deadwood retention favoured the increase of the diversity of saproxylic species. This diversity reached a maximum during the first 10 years following the perturbation, was the lowest 30 years after the stand perturbation, but increased again after 50 years with a different species composition.

The endangered and specialised saproxylic beetle Osmoderma eremita occurs in veteran trees, a habitat particularly threatened by changes in agricultural landscapes. Its conservation requires information about populations and key features of host trees. Surveys of 8,014 trees (pollarded or in hedgerows) were carried out and analysed, based on habitat description (tree level) and spatial information (hedgerow length and distance to the nearest inhabited tree). A suitable cavity was present in 61% of the trees and O. eremita was detected in 42 trees, mainly in Salix (30 observations), the most common tree amongst those surveyed. A small or absent crown was a significant factor in explaining the beetle's presence, as was the distance to the nearest inhabited tree. The largest population of O. eremita, 19 inhabited trees, was found in a wide and continuous area formed by trees with suitable cavities, with distances of less than 250m from each another. Seven smaller areas, with 7, 5 or 1 inhabited trees, were also found. When analysing inhabited trees on a 1km² grid, 17km 2 hosted O. eremita, corresponding to a dense network of 63km of hedges. The presence of O. eremita significantly increased per km² with increasing length of hedges and this variable was thus used to guide forthcoming investigations directed toward Osmoderma. As the hedgerows existing in 1999 had decreased by 6.1% in 2009, it is concluded that the long term survival of O. eremita is under threat. The preservation of trees outside woodlands is urgent and has already started, in connection with Natura 2000 policies. Regeneration and creation of new hedgerows is also ongoing and can be reinforced both by using Salix and by promoting pruning to increase formation of cavities. RESEARCH ARTICLE Launched to accelerate biodiversity conservation A peer-reviewed open-access journalBenoît Dodelin et al.

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