Non-reforestation land (NRL) affects the ecosystem services provided by forests, depending on the state of forest recovery. Although the presence of NRL has been already quantified, long-term monitoring of NRL after abandonment has not yet been carried out. We assessed areas of NRL that were present between 1998 and 2008 on Kyushu Island to identify whether they had been reforested by planting or by natural regeneration as of 2022. We also made a statistical analysis of the factors affecting reforestation and natural regeneration. Replanted and naturally regenerated forests accounted for 20 and 61％ of NRL, respectively. When combined with non-NRL, which was replanted immediately after clear-cutting, we found that 95％ of the clear-cut area had been restored to forest. We found that NRL with low density of Sika (Cervus nippon) or at higher elevations was more likely to be plantation forests. NRL on steep slopes, close to broadleaf forests, or at lower elevations, was more likely to be natural forest. We conclude that intensive forest management is required in NRL that is with high density of Sika, gently sloping, and far from broadleaf forests, because the probability of neither replanting nor natural regeneration is increased in this case.

Japanese oak wilt is an infectious tree disease transmitted by the oak platypodid beetle, Platypus quercivorus. One of the most effective methods to prevent the spread of the disease is to remove infected trees from forests; however, this requires significant on-site efforts. In this study, we evaluated the possibility of reducing the number of newly emerged adults by leaving short logs of varying lengths in the study area. We cut trees affected by the beetles and collected logs of three different lengths (100, 30, and 15 cm), which were left on-site until May 2023. The logs were placed into traps to capture adults, and collections were made monthly in June, July, August, and November 2023. The number of adults per volume collected from the 30 and 15 cm logs was significantly lower than that from the 100 cm logs. While many adults emerged from the 100 cm logs in June and July, few individuals were found in the shorter logs during the subsequent collection months. Our results suggest that leaving short logs (less than 30 cm) in forests could be an effective strategy for managing oak wilt, while reducing the high on-site efforts required to remove infected trees.