Crown dynamics in Pinus resinosa Ait. : analysis and stochastic description of branch production, branch extension growth and foliage dry weight---branch length relationships

Abstract

The development of the crown structure of Pinus resinosa Ait. was analysed in terms of three component processes of tree growth: the number of first order branches per whorl within the crown, the annual extension increments of the main stem and first order branches, and first order branch length - foliage dry weight relationships. Factors regulating these components were analysed and stochastic models to describe them were developed. Thirty-two trees from five different planted stands located in the Quetico Section (L.ll) of the Great Lakes - St. Lawrence Forest Region (Rowe 1972) were examined. These stands represented various site conditions, stand ages, and spacing categories. The number of branches per whorl was weakly correlated with two attributes of the parent structure: the length of the terminal leader at the time of whorl bud inception, and the length of the terminal leader on which the branches occurred as whorl buds. The number of branches per whorl was not related to the age of the tree at the time of whorl bud inception. The binomial probability density function was a suitable model to describe the number of branches per whorl, Extension growth of first order branches varied greatly from year to year. Differences in the extension growth of individual branches were associated with: differences in the annual height increment of the tree, factors governing apical control, and the relative position of a branch within the crown. There appeared to be a potential length which one-year-old branches could attain that was dependent upon the concurrent height increment of the tree. There also seemed to be a potential extension increment for branches after their first growing season that was dependent upon initial branch length and branch age. The observed extension increments of branches were related in a stochastic manner to the potential for branch extension growth to simulate naturally occurring variation. Total branch length was a useful estimator of the total foliage dry weight for branches of the same age.