The spatial genetic structures of three French natural beech stands were analysed using polymorphic enzyme loci. Two methods were used: F-statistics and spatial autocorrelation statistics. Within these stands where self-fertilization rate is 0, a low heterozygote deficit was observed which may be due to a moderate level of mating between relatives. However, no increase of this deficit was observed from one generation to the next. The spatial genetic structuring was low. Within one open stand composed of several patches, founder events are invoked to explain a significant autocorrelation. Within the two other stands, both dense, results are similar to those produced by simulations of an isolation by distance model. The genetic structure seems not to be stable in space and time which may be due to (i) a limited number of generations; (ii) an effective gene flow less limited than hypothesized; and (iii) fertility differences or phenological incompatibilities between individuals.

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Summary — The mating system of beech (Fagus sylvatica L) was investigated using polymorphism at 4 allozyme loci and the multilocus model of Ritland and Jain (1981). Beech appears to be a highly outcrossing species: the outcrossing rate ranges from 0.94 to 1. No significant differences were found in outcrossing rates according to

& Key message The diversity of forest management systems and the contrasted competition level treatments applied make the experimental networks of the GIS Coop, a nationwide testing program in the field of emerging forestry topics within the framework of the ongoing global changes. & Context To understand the dynamics of forest management systems and build adapted growth models for new forestry practices, long-term experiment networks remain more crucial than ever. & Aims Two principles are at the basis of the experimental design of the networks of the Scientific Interest Group Cooperative for data on forest tree and stand growth (GIS Coop): contrasted and extreme silvicultural treatments in diverse pedoclimatic contexts. & Methods Various forest management systems are under study: regular and even-aged stands of Douglas fir, sessile and pedunculate oaks, Maritime and Laricio pines, mixed stands of sessile oak, European silver fir, and Douglas fir combined with other species. Highly contrasted stand density regimes, from open growth to self-thinning, are formalized quantitatively. & Results One hundred and eighty-five sites representing a total of 1206 plots have been set up in the last 20 years, where trees are measured regularly (every 3 to 10 years). The major outputs of these networks for research and management are the calibration/ This article is part of the Topical collection on Mensuration and modelling for forestry in a changing environment.

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