Studies on the silviculture and the management of the Ryukyu-matsu (Pinus luchuensis Mayr) (Department of Forestry)

This study has made in order to investigate the distribution of the Ryukyu-matsu (Pinus luchuensis Mayr) at each cities, towns and village in Okinawa, to establish the plots in many different district in which mother rocks, land features, vegetation, and to research the relation of their growth, stand composition, etc.; more over to be made clear the characteristics of the trees against to the drought hardiness or tolerance of them. To sum up, according to the results of these investigations, it was cleared as follows : 1) The distribution area of the Ryukyu-matsu is 30,634 hectare in total and holds 23% in the total area of forest. The 25% of the Ryukyu-matsu forest is artificial forest, 38% is natural pure Ryukyu-matsu forest, and 37% is mixed forest; in each district, it holds about 84% in Okinawa-gunto, about 9% in Miyako-gunto, about 7% in Yaeyama-gunto. The trees grow well on the soils of the acid and alkaline bedrock zone in all of the islands. 2) The number of the trees in the young stands, investigated 41 plots, is from 1,679 to 24,263 per hectare, and the difference in number among those of plots is great. Generally, the stand density is high at the sunny place, such as, ridge of mountains, top of hissl, where have little crown closure by other plants, and where has been made soil preparating by burning. On the other hand, stand density is low at such a place as a plain of foot or midl-slope of mountains and hills where is surrounded by obstructions, and as a place where the standing trees fairly covered with other plants. 3) Number of standing tree of upper height grade, which is the main constituent of the stand composition, increase or decrease in proporation to more or less of total number of standing trees, but it is recognized that the percentage of upper height grade is decreased according to the increase of the number of standing trees. 4) The total shaded area by crown of closed young stand is constant in spite of quantity of the number of standing trees. The compositive rate of the total shaded area is extremely high in each upper height grade that is over average height grade and is very low in each lower height grade. This tendency is also found in degree of shaded, and in total basal area. 5) In young and matured forest of the Ryukyu-matsu the height, diameter breast high and volume of a tree are the largest on the uppermost height grade. These rates of growth decrease gradually from upper to lower grade, and lower grade, and they are the lowest at lower height grade. These rates extremely decrease on the lower density of standing trees, the higher site and the older trees. This tendency also could be observed in the volume of branches and overn-dried needle-leaf. 6) In each height grade, that are upper, middle and lower, the growth of the diameter breast high and the stem volume of the dominant tree, average tree and inferior tree are recognized that the difference between the former two is small but the inferior tree is very small in comparison with the former two. However, in the stand that density of standing tree is large, the difference of growth among those three is known to be small. 7) The stem volume growth in recent two years of a tree is the largest at the uppermost height grade, decrease gradually from upper to lower grade and is exceedingly small in lower height grade. The more the density of standing trees become smaller, the higher site and the older trees, the more the rate of this reduction get to be large. 8) The stem volume growth of a tree, in recent two years, among those of each height grade have plus correlation to stem volume, volume of branches and oven-dried needle-leaf; especially in the latter, it is very high. 9) During recent two years, the stem volume growth per one gram in dry weight of needle leaf of a tree is, generally, the largest at the middle height grade and become smaller at the upper and the lower in height grade. The product of stem volume per one gram in dry w