Patterns of trunk diameter, tree height and crown depth in crowded Abies stands

The size structure of trees in crowded, even-aged Abies (fir) stands of ‘Shimagare’ or ‘wave-regenerated’ sub-alpine forests is analyzed. Tree-height distributions show consistently smaller variation and less positive skewness than the distributions of trunk diameter and crown depth (tree height minus height of the lowest branch). This difference is associated with changes in the relationships between trunk diameter, tree height and crown depth as stands age. These, in turn, result from self-pruning of the lower foliage crown due to competition for light in crowded stands.