京都大学芦生演習林の土壌調査報告 (第1報)

Abstract

In order to make clear the properties of the forest soil of the KYOTO UNIVERSITY FOREST of ASHIU, about a half of this area was surveyed. The mather rock are shale, clayslate and quartzite, belong to paraeozoic. Topographically, it can be classified into the early or full mature mountains. This area is covered mainly with temperate natural forests〔Cryptomeria japonica (Sugi), Fagus crenata (Beech), Quercus crispula (Japanese Oak), Aesculus turbinata (Tochi) etc〕. The pure stand are partly found, but mainly the mixed stand. Sugi and Beech are mainly found at some higher parts, and Japanese oak and Tochi are at lower parts, along valley. The typical type of forest soil was BD type, it occupy about 85% of surveyed area. The typical soil profiles are shown in Fig. 3-11. BD-d type were found on the ridge of the southern slope overlock the mainstrem of Yura-river. On the southern slope overlock SHIMOTANI, a branch of Yura-river, BD-d type was not found, and on the southern or western site of the highest parts, PD type are found instead of BD-d type. PD type are found in Sugi stand, but in Beech stand there are no PD type, even on the peak of mountain. The soil type which found in Beech stand is all BD type. BE and BF type occupy the lower parts, along valley. As shown above, this area can be classified into the early or full mature mountain, so that the area of BE and BF soil are not so great. As shown in Fig. 1, the precipitation is about 3, 000mm a year, even the most dry season (april ~ May) the mean humidity is above 70%. Accordingly, the area of the dry forest soil is not so great, and BD type is a main typical soil type in this area. BD type occur from peak to valley, and have no relation to the stands. [Figure omitted] To make clear the several soil properties of BD type, soil samples were collected from Sugi stand, Beech stand, and Japanese Oak stand, and from 0--10cm, 10--20cm, 20--40cm and 40--60cm soil depth in each stand. Additionaly the Bl type, that is grass land, were analiesed. Porosity and C contents decrease, with soil depth, and volume weight increase. The rate of decrease and increase are very great compared with the soil of Sugi stand of KITŌ, having high productivity. The order of this rate was follow, the greatest in Sugi stand, next in Beech stand, the smollest in Japanese oak stand. In grass land, even the properties of the surface soil, its volume weight was relatively heavy, and proximetely corespond to the properties of the 40--60cm depth of the Japanese Oak forest (based on fine soil). The depth of A layer was also relatively thin, about 20cm in Sugi stand, and the compactness of Blayer sharply increased with soil depth. Therefore the productivity of this forest soil seemed not so high. When Sugi are planted, suitable site may be BE type or talus, but these soil type occupy only small area. When Sugi are planted at BD type of upper parts of slope, the number of plantation must be increase. PD type occupy only small area, so the Sugi plantation on this soil type must give up. There were some differences of soil properties between tree species, but these were not only due to the differences of tree species, but to the topographie of each stand. That is, the Sugi and Beech stand existed at upper parts of mountains, and Japanese oak stand at lower parts.