When growing Japanese oak (Quercus crispula) on soil-scarified sites, birch is the main competing tree species. It is necessary to remove birches at some time, considering the negative effects of interspecific competition on the oak's growth. On the other hand, a high tree density is desirable for maintaining tree shape (stem straightness), as it controls branching. Therefore, it is necessary to determine the optimal timing for pre-commercial thinning, taking into account the balance between the effects on growth and tree shape. In this study, we investigated the effects of interspecific competition with naturally regenerated Erman's birch (Betula ermanii) on the growth and tree shape of oaks originated from artificial sowing in a 17-year-old soil scarification site. The density of surrounding birches promoted the growth of oaks in the early period (5-11 years), but suppressed its growth in the later period (11-17 years). The mean size of oak was smaller than that of birch at 7 years of stand age, with many individuals showing growth declines 4 to 6 years later. In contrast, the density of birch showed a positive effect on tree shape even at 17 years of stand age. At an early stage, pre-commercial thinning may have a negative effect on growth and tree shape. Rather, the proper timing was thought to be the period of several years after the size of oaks fell below that of its competitors and the decline in growth became evident.

During fumigation treatment of infested pine logs to eradicate Monochamus alternatus larvae, we confirmed instances where the larvae survived and developed into adults that successfully emerged under reduced MITC-gas-concentration conditions. Here, we presented the temporal pattern of adult emergence. Emergence occurred from June 17 to July 11 in the control logs and from June 20 to July 17 in the fumigated logs. The fumigated logs showed a delayed peak of the emergence pattern, with the 50％ emergence day occurring 18 days later than in the control logs. The late emergence of the survivor adults may lead to a prolonged flight season of the local insect population and enhanced utilization of the weakened or dead trees occurring in late summer, potentially accelerating the spread of pine wilt disease.

Large nuts belonging to the Fagaceae family are difficult to store long-term, posing challenges for the production of seedlings and preservation of genetic resources. The aim of this study was to clarify the feasibility of long-term storage of beech nuts using liquid nitrogen. Beech nuts were dried with silica gel to adjust the moisture content in four stages (4.3％ to 13.5％) and sealed in thick plastic bags, stored for 20 years under refrigeration with liquid nitrogen at ultra-low temperatures. No significant change in moisture content was observed during liquid nitrogen storage. Germination rates ranged from 2.0％ to 26.0％, depending on plot treatment, but were significantly lower than the 76.0％ before moisture content adjustment. Furthermore, seedling height and base diameter 5 months after germination were not significantly different from those of seedlings derived from acorns harvested the year before the germination test. These results demonstrate the effectiveness of long-term storage of beech nuts using liquid nitrogen, and indicate their potential for preserving genetic resources of this species.