Abstract
In cold regions with snowfall in Japan, unsuccessful Cryptomeria japonica plantations are often intended to convert into more natural forest in recent years. To improve such a practice, we examined effects of weeding frequency (initial 10-years, vs. only initial 3-years) on density and growth of planted Fagus crenata, the most representative species in primeval forests, and naturally colonized broadleaved species. Although planted F. crenata was suppressed by colonized species, the mortality was lower in the infrequent site (TE) than in the frequently weeded site (WD). The mean diameter at breast height and crown diameter of the F. crenata of 8 year-old were larger in WD, but tree height was significantly large in TE. Moreover, the rate of snow pressure damage was higher in WD. Regarding the colonized broadleaved species, Betula maximowicziana and B. ermanii disappeared completely in WD in the study period, probably because of their sensitivity to aboveground cuttings. Only Prunus grayana, a species with high sprouting ability, was remained in the lower canopy layer. In contrast, in TE, these three species were established with F. crenata, forming the stratified canopy structure. We strongly recommend reducing the weeding frequency to restore natural stand characteristics in the conversion management in this region.
