2024 Volume 106 Issue 8 Pages 225-232
Selection cutting has been carried out widely in natural forests in Hokkaido. However, the expected natural regeneration was not generally obtained, resulting in a degradation of natural forest resources. As one of the solutions, soil scarification with heavy machinery has been carried out to remove dwarf-bamboo that inhibit tree regeneration. However, its implementation is limited in practice because the timing of cutting (winter) and regeneration assistance (summer) is different. It is technically and costly difficult to re-approach the target points (i.e., cut stumps) scattered in the forest in summer, and the operation may disturb advance regeneration. Therefore, in this study, we attempted to conduct scarification during the snow season (winter scarification) by extending an operation to dig up snow around trees with heavy machinery in advance for cutting in winter (preparatory snow removal). The operation cost and the effects on natural regeneration were compared with control (no-scarified area) and standard scarification area (summer scarification). If we compare only the operation for regeneration assistance, the costs could be reduced to one-third of the summer scarification. In about 90％ of the winter scarification areas, the regenerated saplings (mainly Betula ermanii) overtopped the surrounding dwarf bamboos (average height 145 cm), and in about 70％ of the areas, the sapling density exceeded 1,000 trees/ha. We conclude that the winter scarification could be an option associated with selection cutting as one of the key operations to re-establish natural forest management in Hokkaido.
