Leaf development and stem growth of ash (Fraxinus excelsior) as affected by tree competitive status.
Leaf development and stem growth of ash were studied during 1993, in an experimental area installed in a mixed natural broadleaved stand in the state forest of Amance, NE France, where 20-24 yr old ash trees formed part of the dominant layer of the stand. Seventeen trees were selected to represent the range of diameter classes and competitive conditions. For each sample tree, stem girth was measured at several heights above the ground, at the beginning and at the end of the growing season, to evaluate stem volume growth. Crown projection surface area before the growing season and tree height growth were used to estimate a foliar volume. Total leaf dry weight of each tree was obtained by collecting leaves in autumn, and total leaf area was obtained from a sample of leaves. To collect leaves without cutting down the trees, tree crowns were wrapped with nets before leaf fall, from a truck equipped with a nacelle mounted on an articulated arm. Leaves were collected as they fell and accumulated in the bottom of the net. Size relationships were established between foliage biomass and stem and crown dimensions (basal area, crown projection area, foliar volume), between leaf area and foliage biomass, and between bole volume increment and basal area. A basic growth equation was established. This equation shows that consideration of bole surface area is essential for understanding the relationship between annual stem volume increment and foliage biomass. Competition between trees was responsible not only for the differences observed in tree dimensions and growth, but also for the differences in foliage efficiency expressed as bole volume increment per unit of foliage biomass.