A study on young beech tree release in uneven-aged stands

In uneven-aged stands, foresters often focus on the change in quality and vigour of a few young trees per hectare called future trees (7.5cm<dbh<17,5cm). A central issue is to determine whether a thinning at a given time would be profitable for these trees. For seedlings and saplings, many studies have shown that diameter growth is closely related to light availability. For these small development stages, relevant indicators of vigour, such as the living crown ratio, the plagiotropy of branches, the slenderness, and the crown projection area already exist. Nevertheless, light availability for trees appears difficult to evaluate in uneven-aged stands and the validity of the indicators has not yet been clearly assessed for later developmental stages. Finally, most studies do not take into account the quality features of the trees (epicormic shoots, straightness). Actually, current decisions are very often empirical. In 2006 the French Forest Service (ONF) and the National Research Institute of Agronomy (INRA) began a study in several uneven-aged mixed stands (i) to define morphotypes of small beech trees for the northern part of France and (ii) to release these morphotypes by local thinning to determine their potential reactivity. Here, we present the methodology used to build morphotypes and to release trees in the experiments.