Crown architecture of stand-grown sugar maple (Acer saccharum Marsh.) in the Adirondack Mountains.

Abstract

Leaf and crown morphology of shade-tolerant sugar maple (Acer saccharum Marsh.) were examined to test the hypotheses (1) that leaf area exhibits significant plasticity both within and between crown classes and individual tree crowns and (2) that leaf area is accurately predicted from estimates of crown volume. A total of 18 trees, ranging from 3.3 to 43.4 cm dbh, were felled and dissected into upper, middle, lower, and below-crown layers, for measurements of leaf, bark, and xylem dimensions. For dominant trees only, bark thickness and xylem radii were higher within the crown than below the crown. Cumulative leaf area index increased with decreasing stratum height at similar rates in all trees, except for two trees that were located in the understory. Area leaf weight declined with decreasing stratum height within the crown of all except four overstory trees. These four trees showed an increase with decreasing stratum height, i.e., leaves were heavier per unit area in the lower crown stratum and below the crown than they were at mid-crown. Within-tree leaf area density was usually higher in the upper crown of overstory trees and in the lower crown of understory trees. Total crown volume was the best predictor of whole-tree leaf area, but it was only slightly better than dbh.