Compétition entre classes sociales chez le chêne sessile et le hêtre

Abstract

Single species, even-aged stands of beech or sessile oak are frequently in conflict from the standpoint of dynamics (speed of growth), the factors that determine wood quality (effect of fast/slow growth regimens) and the impact of thinning (capability of remaining trees to benefit from interventions). The article deals with the last point by analyzing competition between social ranks : how thinning regulates competition, what its effect is on differential growth of social classes. More localized aspects of competition (stimulating effect of localized thinning, or trimming, for the benefit of final crop trees) are not considered. The analysis was performed on networks of permanent plots established between 1880 and 1935. It shows up the common points between these species that are appropriately referred to as social : they form highly structured systems in which individuals which rank highest socially are those that grow the fastest. A simplified model is used to more accurately quantify the relationship between social rank and growth. The two species are found to differ very significantly : for beech, surplus growth afforded by thinning is all the more pronounced the higher the tree's initial status. For oak, the benefits of thinning are uniform whatever the trees' social status, at least in terms of basal area. These differences in behavior are discussed with reference to competition for light and for soil resources, particularly water.