The risk of windthrown trees due to typhoons has increased because of climate change, making it imperative to be able to rapidly assess the extent of damages. Typhoon No. 21, which landed on the Japanese archipelago in September 4, 2018, was used for a survey of woodlands in the Natural and Cultural Gardens located in the Expo’70 Commemorative Park (Suita, Osaka Prefecture). By comparing a Digital Surface Model (DSM) obtained by processing data sets on two dates, before the typhoon on July 11, 2018, and after the typhoon on September 26, 2018, using Structure from Motion, I was able to extract the extent of the windthrown trees gaps caused by the typhoon. The correlation between the gap-patch area and breast height cross-sectional area was overall higher than correlation between the gap-patch area and number of trees from within the gap patch. I was able to extract gaps formed by fallen trees for a difference of ≥ 6 m between the two DSM periods. The total gap-patch area generated by the typhoon was 6,926 m², which was equivalent to approximately 64％ of the gap area artificially caused within the same area over 17 years between 2000 and 2017. Taking regular data sets with UAV will be effective for forest monitoring.

Kudzu (Pueraria lobata) is native to Japan and one of most noxious woody vine species causing adverse effects on ecosystems due to its strong reproductive ability. Its eradication from urban-rural landscape, especially revegetated areas is urgent. The ecological effects of five successive treatments (non-treatment, herbicide imazapyr, digging, biannual cutting, and shading) on the coverage of kudzu and composition of cut-slope vegetation were assessed for three years between June and December each year. Among the five treatments, a shading treatment was conducted from the second-year experiment on behalf of an annual cutting. Eradication of kudzu was rapidly achieved after implementation of digging and shading treatments. Especially, in the case of digging method, there is no need for continuous treatment after the initial one. Furthermore, although vegetation cover, number of species, and their life cycle composition diversity on cut-slopes increased in digging treatments, these recovery after shading treatment were not found throughout the experimental periods possibly due to the short non-shading treatments. Little eradication effects of other treatments on kudzu were found. From these results, we suggested that, among the treatments selected, the digging treatment, regardless of its high initial treatment costs is most effective to eradicate the noxious liana kudzu and taking into account recovery of vegetation on cut-slopes.

Ginkgo biloba, which grows widely in Japan, was introduced from China; however, the detailed process of its spread across Japan remains unclear. Therefore, in this study, we evaluated the spread of G. biloba in Japan based on the genetic variation between giant trees from different regions. Giant trees are thought to exhibit genetic variation similar to the variation present in the early stages of introduction from China to Japan. We collected leaf samples from giant ancient trees over 8 m in girth at breast height from Kyushu to Tohoku regions. We analyzed 8 microsatellite markers in 199 samples from 180 individuals. From this analysis, we detected 8-21 alleles in 8 loci and identified 142 genotypes. Of the genotypes identified, 13 were shared by 70 individuals. We considered individuals sharing a genotype as clones. Since some individuals sharing genotypes were geographically separated from each other, it is possible that not only seeds but also cuttings were used for the propagation of G. biloba in Japan. Genetic diversity (H_E) was 0.57-0.82, while allelic richness (AR) was 4.51-8.49. We observed low H_E and AR values in eastern Japan. Therefore, G. biloba may have been transported from China to western Japan, and it is likely that a small percentage of trees further disseminated to eastern Japan.