Quantitative morphometry of the branching structure of trees

Abstract In this morphometric study of an apple tree and a birch tree every segment of a branch has been measured with respect to diameter and length, and the number of buds counted on the birch tree. A computer was used to calculate the number of end branches and buds supplied by every branch, to calculate the summed length from ground level to every branch and to order the branches by the method of Strahler. When numbers of branches, buds and end branches, and also diameters, are plotted on logarithmic scales against order approximately linear plots are obtained. The length plots are much less regular and the distributions of summed length are different in the two trees, suggesting that variation in length contributes significantly to the different forms of trees. The findings are similar to those in other naturally occurring branching systems, which together suggest that they are formed in a non-random fashion. Finally the difficulties of measuring such systems by sampling methods are indicated.