Early growth of hinoki (Chamaecyparis obtusa) trees under different topography and edge aspects at a strip-clearcut site in Kyushu, Southern Japan

The positive and negative effects of the residual stand edge at a strip-clearcut site were examined on the initial growth of hinoki (Chamaecyparis obtusa) planted in areas with diverse topography. On the south edge, the gap light index was lower than on the north edge and strip center; however, the vapor pressure deficit was also lower than on the north edge and strip center, which resulted in lower physiological stress of hinoki on the south edge. Tree size on the south edge did not exceed that on the north edge and strip center. These results indicated that low light conditions due to residual trees negatively affected growth on the south edge even under the positive effect of microclimate alleviation. In valley, tree size in the second year after planting was smaller than on ridge and slope; however, tree growth during the following 2 years was higher in valley. Surface soil in valley was thinner with rockier substrates than on ridge and slope; that is, soil sedimentation type and substrates influenced the initial growth of hinoki with undeveloped roots, and after that, topography started to influence growth, probably because hinoki roots penetrated into deeper soil, which is influenced by the water gathering capacity of the valley. The initial growth of hinoki at the strip-clearcut site was predominantly affected by light rather than microclimate alleviation. This alleviation is expected to disappear when hinoki trees planted in the strip center grow enough to give additional shade to slow-growing edge hinoki.