[en] Aim of the study: We analysed the effects of thinning intensity and canopy type on Scots pine growth and stand dynamics in a mixed Scots pine-beech forest. Area of the study: Western Pyrenees. Material and methods: Three thinning intensities were applied in 1999 (0, 20 and 30% basal area removed) and 2009 (0, 20 and 40%) on 9 plots. Within each plot, pure pine and mixed pine-beech patches are distinguished. All pine trees were inventoried in 1999, 2009 and 2014. The effects of treatments on the tree and stand structure variables (density, basal area, stand and tree volume), on the periodic annual increment in basal area and stand and tree volume, and on mortality rates, were analysed using linear mixed effects models. Main Results: The enhancement of tree growth was mainly noticeable after the second thinning. Growth rates following thinning were similar or higher in the moderate than in the severe thinning. Periodic stand volume annual increments were higher in the thinned than in the unthinned plots, but no differences were observed between the thinned treatments. We observed an increase in the differences of the Tree volume annual increment between canopy types (mixed < pure) over time in the unthinned plots, as beech crowns developed. Research highlights: Moderate thinning is suggested as an appropriate forest practice at early pine age in these mixed forests, since it produced higher tree growth rates than the severe thinning and it counteracted the negative effect of beech on pine growth observed in the unthinned plots. (Author)

[en] We investigate the probability distribution P_N(r) of the radius of gyration r of a polymer chain of size N with excluded-volume interactions at infinite temperature. This function shows the geometric contribution to the tricritical coil-globule transition of self-avoiding walks; it indicates that the relevant order parameter t of the transition is a power of the density ρ=Nr^-d. The theoretical form of the distribution P_N(t) of this order parameter is deduced from scaling arguments, and supported by numerical simulations. Intending to probe the contribution of the different subsets of conformations, namely, globule, coil and stretch, we supplement P_N(t) with a formal Boltzmann factor; this model undergoes a tricritical coil-globule transition which is solved exactly. We show a nontrivial finite-size scaling for P_N(t) and analyze its convergence toward the thermodynamic limit. Due to the presence in P_N(t) of a diverging factor t^c with c<-1, this convergence happens to be tragically slow. As a result, the scaling behavior observed in numerical simulations is qualitatively different from its thermodynamic limit, and we relate the critical exponents of the geometric transition in the thermodynamic limit and the effective exponents observed at finite size. copyright 1997 The American Physical Society