Ingrid Seynave

Significant differences and curvilinearity in the self-thinning relationships of 11 temperate tree species assessed from forest inventory data

IntroductionIn pure and even-aged stands, the allometry between mean tree size and maximum stand density—or self-thinning relationship—has long been considered a constant among tree species. Although the self-thinning allometric coefficient has been shown to be species-dependent, estimates available for a given species also differ. Whether this coefficient truly varies across species thus remains an open issue. A potential cause of variation in the coefficient may lie in a departure from the allometric assumption in the self-thinning relationship.MethodsWe analysed the species dependence of the self-thinning relationship for 11 temperate and Mediterranean tree species growing in pure and even-aged stands in France based on the French National Forest Inventory (NFI) data. Self-thinning relationships were fitted using a ‘stochastic frontier’ technique. Pairwise comparison tests of the self-thinning allometric coefficients were implemented. We also investigated the allometric nature of the relationship by testing a linear and a curvilinear model of log density against the log quadratic mean diameter.ResultsSelf-thinning relationships were clearly evidenced from the NFI data and displayed significant differences between species. The curvilinear model was significantly more accurate for 7 out of 11 species and depicted a concave relationship, suggesting a decrease in self-tolerance over ontogeny.ConclusionAs a major finding, the self-thinning relationship significantly varies across species. We emphasise the need to consider a high number of species to show such specific variations in the self-thinning relationship. Another important outcome is that the self-tolerance depends on the developmental stage.

PRÉSENTATION DU PORTAIL WEB SILVAE : SYSTÈME D’INFORMATIONS LOCALISÉES SUR LA VÉGÉTATION, LES ARBRES ET LEUR ENVIRONNEMENT

The purpose of the SILVAE portal (http://silvae.agroparistech.fr/home/) is to give a broad-based population access to spatial data for the whole of metropolitan France about forest plant species —mostly tree— together with the main factors that determine their ecology. The available information is classified by theme. The information concerns the bibliographic references of the AgroParisTech documentation centre in Nancy, and the LERFoB data: the phyto-ecological records made in the field found in the EcoPlant data base and continuous geographic spatial data extracted from Digitalis data base. Before using the portal, it is important to read the associated descriptions and scientific publications so as to appreciate the limitations in use inherent to each type of data. SILVAE will be regularly enriched so as to provide managers, researchers and students with up-to-date information

Le portail web SILVAE met à disposition des informations écologiques et forestières spatialisées

Le portail SILVAE (système d’informations localisées sur la végétation, les arbres et leur environnement) est un site web qui a pour vocation la mise à disposition gratuite et pour un large public de données géographiques issues du centre de documentation d’AgroParisTech Nancy ou du LERFoB (Laboratoire d’Études des Ressources Forêt Bois, unité mixte de recherche AgroParisTech-INRA). Il propose des informations concernant les espèces végétales forestières, essentiellement arborées, et les principaux facteurs déterminant leur écologie, pour une gamme d’échelles pouvant aller de la France entière jusqu’au massif forestier. Ce site, financé par le ministère de l’Agriculture, de l’Agroalimentaire et de la Forêt ainsi que la région Lorraine, est accessible au public à l’adresse http://silvae.agroparistech.fr/home/.

Mise en place d’un réseau de suivi des écosystèmes forestiers en limite des départements de la Meuse et de la Haute-Marne

A network for the long term observation of forest ecosystems has been established in the Observatoire perenne de l’environnement (Permanent Environmental Observatory) created by the National Agency for Radioactive Wastes. The network is located at the boundary between the Meuse and Haute-Marne departements and comprises some hundred permanent inventory points. The forests in the network consist in 75% of high forests at various stages of development, half of which are adult stands. Five major soil types were identified in the observation network and the forest sites accommodate a rich variety of species, although the variability of the environment is limited on the scale of the network as a whole. Land utilisation has changed since the beginning of the 19th century, with the contraction of cultivated areas that tend to be taken over by forests.