GROWTH AND MORPHOGENESIS IN THE CANADIAN FOREST SPECIES: IV. RADIAL GROWTH IN BRANCHES AND MAIN AXIS OF PINUS RESINOSA AIT. UNDER CONDITIONS OF OPEN GROWTH, SUPPRESSION, AND RELEASE

The analysis of growth of a pine tree has been extended to include the primary branches, and this paper reports observations on radial growth, as expressed by ring width.Trees from contrasting situations are compared, and the deliberate release of one tree from suppression permits the attribution of specific changes in growth to the change in external condition of the tree.The primary branches provide a series of axes that automatically undergo a change in nutritional status, although the distal portions of all of them are produced simultaneously. Every primary branch is initiated at the apex of the tree and each year is overlaid by one more whorl of branches; so it advances to a relatively lower position in the tree each year, and itself adds one more internode.The upper branches and those portions of lower ones that were formed while near the top of the tree repeat the pattern and configuration of growth in the main axis. Advance of a branch to an inferior position is associated with severe suppression ...