THE BRANCHING HABITS AND LIFE-HISTORY OF WOODY-PLANTS

Medium to small woody plants of North America tend to look leggy as a result of their relatively thick lateral branches. In contrast, trees that regularly attain great size have relatively thinner, shorter laterals. These differences in body plan arise from differences in the intensity and frequency of inhibition of lateral branches. This correlation between maximum attainable size and branching habit supports several lines of speculation concerning the limits to size in woody plants. A simple verbal model, based on the economics of photosynthetic gain versus structural costs, accounts for both the observed limits and the correlation between size and branching habits. We conclude that life-history differences may account for much of the unexplained variation in the arrangement of branches in woody plants.