EVIDENCE THAT TEMPERATE EAST NORTH AMERICAN EVERGREEN WOODY PLANTS FOLLOW CORNER'S RULES

Summary Coener's rules, first developed for tropical trees, predict a spectrum of woody plant forms, from ones with small leaves, thin twigs (first-year shoots) and many branches, to ones with larger Waves, thick twigs and few branches. These rules were confirmed for nine broad-leaved and 12 needle-leaved evergreen woody plants of temperate eastern North America: for each of these groups, leaf size was positively correlated with twig cross-sectional area and both of these were negatively correlated with the number of twigs needed to bear 104 cm2 total leaf area. When compared to deciduous trees, characterized in a previous study, broad-leaved evergreens had leaves that were 85% smaller at a given twig thickness and needed 750% more twigs to bear a given total leaf area (at least when leaves older than 1 year were ignored). Needle-leaved evergreens bore relatively small leaves but large numbers of leaves per first-year shoot; they bore fewer twigs per 104 cm2 total leaf area than broad-leaved evergreens, but more than broad-leaved deciduous species. Broad-leaved deciduous trees were characterized by relatively large leaf sizes as a function of twig cross-sectional area and low numbers of twigs per 104 cm2 total leaf area. Although Corner's rules are a significant index of plant form, a full resolution of the differences between deciduous and evergreen species awaits further study.