Crown spread patterns for five deciduous broad-leaved woody species: Ecological significance of the retention patterns of larger branches

Abstract

Patterns of crown spread and branch retention of two shade-intolerant species (Betula platyphylla and B. maximowicziana) were compared with three more tolerant species (Quercus mongolica, Acer sieboldianum and Magnolia obovata). Branching height (height of the lowest living branch) rose more rapidly with age for the two Betula species than for the shade tolerant species. Branching heights of A. sieboldianum and M. obovata were similar, irrespective of tree height and age, and larger trees tended to produce wider crowns than the Betula species when trees of similar height were compared. In all species, the branch basal area (cross-sectional area of a branch at its base) and the leaf area per branch generally increased as the branch position on a stem became lower. Therefore, retaining larger branches contributed significantly to the support of a larger leaf area per tree. The number of larger branches (branch basal area > 80 cm2) for both Betula species was significantly smaller than that of the shade tolerant species. The branch retention pattern of Betula species was probably a consequence of intolerance of the leaves to shade. The decline of Betula species with forest succession is likely to occur through their inability to retain branches with a large base area in closed forests.