Comparison of nutrient dynamics along a slope between artificial Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) forests

摘要

The purpose of this study was to clarify the effects of different species on the nutrient dynamics and soil fertility in each slope position (upper, middle, lower). This study site was planted with Japanese cedar, and the adjacent area was planted with Japanese cypress along slope from the ridge to the stream. We investigated the soil chemical characteristics, the amounts and nutrient contents of the forest floor and litterfall, the amounts of dissolved elements in the precipitation, the throughfall and percolated water through 0 (under forest floor), 25, and 50 cm depths of the soil and the annual amount of nitrogen mineralization in the soil for the cedar and cypress forest on each slope. The turnover rate (amount of forest floor/amount of annual litterfall) in the cedar forest was almost the same as that of the cypress forest on the upper and middle slopes, but was about 3 times greater than that in the lower slope. The amounts of available nutrients in the cypress forest supplied to plants were equal to or greater than those in the cedar forest on the lower slope, but the percolated nutrients available through the 50 cm soil depth in the cypress forest were greater than those in the cedar forest. This is thought to be because the cypress forest had a lower nutrient absorption than the cedar forest on the lower slope.