4 Discussion
Competition for resources among plants generates stress such that some plants adapt to survive while others gradually die under the stress. To understand the mechanism of plant performance differences under intraspecific competition, we studied the scaling relationships at the individual and branch level from the perspective of canopy structure. The results indicate that with the deterioration of tree growth vigour, intraspecifically tree growth in height with respect to trunk diameter (i.e. the H -Dscaling exponent) decreased, while branch growth in length with respect to diameter (i.e., the L -d scaling exponent) increased. This research improved our understanding of canopy architecture and the mechanisms underlying competition-induced tree mortality.