Growth of tree diameter and stem taper as affected by reduced leaf area on selected branch whorls

Abstract

Leaf area on branches is linked to the stem through hydraulic and physiological functions. We investigated whether this relationship extends to growth responses by examining coordinated growth between leaf area on selected branches in the crown and growth in form and taper of the main stem. The growth impact of leaf area carried on individual branch whorls on the stem profile and internodes was tested using a series of defoliation and shade treatments. The data were analyzed using a linear mixed-effects model relating relative diameter to the relative height of the measured internodes. Defoliation and shade treatments on selected branches significantly affected the stem profile compared with untreated trees. The effect of reduced leaf area due to defoliation and shading of branch whorls was localized to internodes immediately below or above treated whorls. The stem profile showed curvature in the regions affected by reduced leaf area. These findings demonstrate that branch and stem growth is sensitive to minor changes in leaf area. The results emphasize the localized contribution of branches to stem growth.