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International audience; Deadwood, whether expressed in volume, diversity or continuity, is nowadays widely acknowledged as being an important component of forest ecosystems, and has therefore been addressed in most recent studies dealing with forest conservation and management. However, and despite the growing use of the concept of naturalness in the management plans of French forest reserves, the dynamics of deadwood remains greatly unknown in West European temperate forests. In this context, and in order to answer a growing demand arising from the managers of forest reserves, a specific long-term monitoring scheme has been implemented in all main forest habitats since its launch in 2005. Our talk will present some preliminary results of this country-wide monitoring based on data from 36 Biological Reserves and 18 National Nature Reserves. In this network, a comprehensive data set of living and dead tree measurements has already been collected on >5.000 permanent plots covering a wide range of situations. Although most of the sites showed significant amounts of deadwood (mean: 38.1 m3/ha), we will focus our presentation on the important differences that were found between sites and within sites. We analyze the relationships between these differences and habitat types, altitude and management practices. Future surveys will allow us to better understand the driving forces behind these differences and will provide us with management tools to assess how these values will/can increase in the future.

International audience; Deadwood, whether expressed in volume, diversity or continuity, is nowadays widely acknowledged as being an important component of forest ecosystems and has therefore been addressed in most recent studies dealing with forest conservation and management. However, and despite the growing use of the concept of naturalness in the management plans of French forest reserves, deadwood dynamics remain greatly unknown in European temperate forests. In this context and to answer a growing demand arising from reserve managers, a long-term monitoring scheme has been launched in 2005. Preliminary results from 42 French forest reserves will be presented in this talk. A comprehensive data set of living and dead tree measurements have so far been collected on more than 4000 permanent plots. Sampling is systematic but the density of plots is adjusted to the reserve size, habitat diversity and management practices. Overall, French forest reserves host an average of 35.1 m3/ha of deadwood. More than 2/3 of the reserves had deadwood volumes between 20 and 40 m3/ha, and were considered deadwood rich. For more than 1/3 of these reserves, the estimated volume was even greater than 40 m3/ha, indicative of forests growing under nearly natural conditions. Although most of the reserves showed a significant amount of deadwood, the gap with old-growth forests is still of great magnitude. The following surveys should allow us to better understand these differences.