Abstract
This report presents the vertical distribution of the stem cross-sectional area increment of the hypothetical tree with average stem size and form in even-aged stands of Hinoki cypress (Chamaecyparis obtusa). Datasets from five long-term permanent sample plots established on the Kii Peninsula, central Japan, were used. In these plots, total height and diameter at breast height (DBH) of every living tree have been continuously measured several times at about 5- or 10-year intervals for over 40 years, but stem form has not been measured. The average relative stem curves determined for Hinoki cypress stands in Nara Prefecture were applied. The stem form of the hypothetical tree at each measurement was estimated by substituting the average total height and DBH into the average relative stem curve. The vertical distribution of the stem cross-sectional area increment was calculated as the difference between the stem forms at the beginning and end of the successive measurements. The vertical distributions in these plots were broadly divided into three types based on increasing trend downward in its lower portion: increase, constant, and decrease. Furthermore, variations in form of the vertical distribution were associated with intraspecific competition within the stands. In conclusion, the vertical distribution of the stem cross-sectional area increment presented here would be a useful indicator for planning stand density management.
