Abstract
We evaluated the relationships of some environmental factors to the success of Cryptomeria japonica afforestation and the degree of regeneration of hardwoods in C. japonica plantations in three watersheds in Akita Prefecture, a snowy region of northern Japan. Both stem density and canopy height of C. japonica declined as elevation increased: at elevations of more than ca. 650-m, heights fell below the threshold for the lowest site productivity class (least economical), and the densities were less than standard values. Various hardwoods such as Swida controversa, Eleutherococcus sciadophylloides, Clethra barbinervis, Prunus grayana, Fagus crenata, and Quercus crispula had regenerated in C. japonica plantations in all three of the surveyed watersheds. As elevation increases, it becomes harder to establish C. japonica plantations and easier for hardwoods to grow, but at much higher elevations, dwarf bamboos grow vigorously and inhibit the regeneration of hardwood trees. At elevations of more than 870-m, not only the establishment of C. japonica plantations but also the regeneration of hardwoods have been unsuccessful. We conclude that it is effective to give priority to areas at elevations of less than 650-m, which roughly corresponds to 2.0-m in maximum snow depth, for the efficient management of C. japonica plantations as commercial forests on a watershed scale. For plantations located in higher elevations, it is necessary to shift priority from commercial to environmental purposes.
