& Context Biomass prediction is important when dealing for instance with carbon sequestration, wildfire modeling, or bioenergy supply. Although allometric models based on destructive sampling provide accurate estimates, alternative speciesspecific equations often yield considerably different biomass predictions. An important source of intra-specific variability remains unexplained.• Aims The aims of the study were to inspect and assess intraspecific differences in aboveground biomass of Pinus brutia Ten. and to fill the gap in knowledge on biomass prediction for this species.• Methods Two hundred one trees between 2.3 and 55.8 cm in diameter at breast height were sampled throughout the easternand southernmost natural distribution area of P. brutia, in Middle East, where it forms different stand structures.Allometric equations were fitted separately for two countries. The differences in biomass prediction at tree, stand, and forest level were analyzed. The effect of stand structure and past forest management was discussed.• Results Between-country differences in total aboveground biomass were not large. However, differences in biomass stock were large when tree components were analyzed separately. Trees had higher stem biomass and lower crown biomass in dense even-aged stands than in more uneven-aged and sparse stands.• Conclusion Biomass and carbon predictions could be improved by taking into account stand structure in biomass models.

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International audienc

Pinus brutia occurs in the Eastern Mediterranean region and is the most widespread conifer species in Middle East. It is important for multi-purpose forestry owing to its high ecological value and economic importance. To model the stand dynamics of P. brutia, 133 semi-permanent sample plots were placed in 10 to 166 year-old stands in Syria and Lebanon, covering the whole range of variation in site quality, stand age and stand density. Site index, distance-independent diameter increment, height and self-thinning models that included country effects were fitted to the data. The site index model was fitted using the guide curve method. The data for 10-year diameter growth model consisted of past growth measurements of all trees within the 133 plots. Diameter growth was modelled using variables representing site, size and competition. The self-thinning model was developed by estimating the maximum number of trees per hectare as a function of mean diameter and site index. These are the first cross-border models in Middle East enabling forest growth and yield predictions and stand dynamics simulations on an individual-tree basis. Such models will allow, with the aid of optimization techniques, finding the optimal forest management for P. brutia forests based on different management objectives.

We compared plant species diversity in cut (coppiced) and uncut (22 yrs old) chestnut stands of the Cévennes in southern France over a 6-year period by measuring species richness, Shannon-Weaver biodiversity index, Leaf Area Index (LAI), and life form spectra. Species richness increased six-fold immediately after the clear-cut from 5 species in the old coppice stand before the clear-cut to 30 species 2 years after the cut, but subsequently decreased over the 6-year period to reach 15-16 species in a 100 m" plot (n = 15). The Shannon-Weaver diversity index behaved like species richness. LAI increased during this period, but there were no statistically significant relationships between the diversity indices and LAI. The life form spectra were also greatly modified after the clear-cut. These changes mainly concerned the number of hemicryptophytes which increased significantly. This behavior is very different from that observed in old field succession where therophytes (annuals) are the first invaders of the open areas. Finally we discuss the consequences of various land use practices on the conservation of plant species diversity in these two types of chestnut dominated ecosystems.