To obtain straight, tall (＞4 m) stems of Melia azedarach Linn. for timber production, bud pruning is performed. To estimate the effect of bud pruning on biomass distribution, we applied the stratified clip method to the aboveground parts of a 16-year-old M. azedarach stand and determined the allometric relationships among stems, branches, and leaves. Trees with relatively long straight stems and high clear lengths had smaller diameter at breast height (DBH) values. However, in even lower clear-length trees, the secondary branches died, such that leaves were distributed mainly in the upper layer of the crown. This effect may be a factor in the stem diameter growth suppression observed after the 10^th year. For M. azedarach, however, we used the standing-tree volume table for type-1 hardwoods in Western Japan, which includes the curved part of the stem. Therefore, we derived one allometric equation to estimate the total volume of straight stems and another to estimate the volume of knot-free stems with pruned buds at 0.2-4.2 m in height, which are useful for efficient timber production. These allometric equations will allow practical calculations of stem volume in bud-pruned M. azedarach for forestry applications.

As the world's forest area continues to decline, China's forest area has consistently increased since the 1980s. In this research, we clarified the driving force behind this by focusing on the socio-economic factors of China. There is much previous research on the relationship between socio-economic factors and forest resources in various countries. However, the methods used for research in this field are mainly panel data analysis, and the results produced using such tests, for example unit roots and cointegrations of time series data, are limited. In this research, we used the time series data for the last 40 years on forest area and socio-economic factors in China, and we used an autoregressive distribution lag (ARDL) model considering the stationarity of variables and the cointegration relationship. Unit root tests show that all variables are either stationary or becoming stationary after the first differencing. The estimation results show that the change rate of GDP per capita has a positive impact on the change rate of forest area in the short-run but a negative impact in the long-run, and that the change rate of rural populations has a negative impact in both the short- and long-run. It was also shown that the change rate of urban population and foreign direct investments in China have a positive impact on forest coverage rates in the short-run.

In this study, we conducted a questionnaire survey on forest awareness and forest experience in Japan and China to clarify their characteristics and relationships. The results of the analysis showed that there were clear differences in forest awareness and forest experience between Japan and China. In Japan, there were differences in forest awareness and forest experience, based on age group. In contrast, in China, there was no difference between generations in forest awareness and forest experience. In China, the same “tree-planting experience” of compulsory afforestation and the “conceptual experience” from learning influenced the common forest awareness among all generations. Considering the transition in the relationship of people with forests in Japan and China, it was found that forest experience during the childhood of each age group influenced the forest awareness both in Japan and China. In addition, based on region group there was no difference in forest awareness and forest experience in Japan and China. This suggests that there is a need for more detailed forest environmental education and forest experience programs tailored to the forest conditions of each region.

This study elucidated the occurrence and process of unauthorized logging in the southern Kyushu region of Japan. In 2020, a questionnaire survey was conducted among 502 forest owners living in a municipality that reported unauthorized logging, and 161 responses (32％) were received. Results from the survey revealed that 7％ of owners sustained damages from unauthorized logging, whereas 12％ of owners were unaware of any damages that had occurred. The results from classifying and comparing the damages caused by unauthorized logging into three categories, including damaged owners, non-damaged owners, and non-cognitive owners, indicated no differences in the cadastral survey progress between damaged and non-damaged forestland. However, it was suggested that unregistered forests might be vulnerable to damage. Owners unaware of the damage were less aware of the forest area they owned. Further, interviews with seven victims of unauthorized logging confirmed that the malpractices of unauthorized logging included unreported logging, boundary invasion, and forging the logging notification. Confirming the submitted logging notification on-site was deemed necessary to resolve the issue of forging notifications. Therefore, this study raises concerns about the spread of unauthorized logging in forests where owner awareness is low.

For early detection of pine trees damaged by pine wilt disease and prevention of their oversight in field surveys, we conducted time-series measurements and field surveys in a parcel (about 130 × 40 m) of coastal black pine groves by using a UAV equipped with an optical camera and a UAV equipped with a multispectral camera. By visual interpretation of NDVI and RGB images, five, three, three, and six areas were identified with reduced NDVI or discolored tree canopy on 31 July, 15 August, 28 August, and 18 September 2019, respectively. Of the 26 pine trees that were confirmed during the field surveys by 17 September to be damaged by pine wilt disease, 16 were found by reading aerial images in or near these 17 areas (detection rate: 61.5％). Although there is a limit to detection by reading aerial images, our detection of about 60％ of pine trees damaged by pine wilt disease will support the conducting of a detailed field survey of the surrounding areas, thereby enabling us to prevent oversight by cross-checking from the air and ground. The results also suggested that NDVI images may be able to detect damaged trees about 2 weeks earlier than RGB images.

We conducted dropping experiments of the root ball of sugi (Cryptomeria japonica D. Don) cuttings grown in multi-cavity containers in order to examine the effectiveness of root coverage of root ball surface (CRBS) as an indicator of destructive strength of container-grown root balls. Root balls of intact cuttings were dropped for three times from 1 m height, and the soil medium detached at each time was separately collected and weighed. CRBS were obtained by image analyses of the photographs of root ball surface as a percentage cover of the roots. Generalized linear models performed for the mass of detached soil medium (RDSM) demonstrated that varying soil detachment of containerized root-balls was largely explained by CRBS. The containerized cuttings showed exponential decrease of detached soil medium along the increase of CRBS as well as root mass at each of the three droppings, indicating that the CRBS is a good indicator of the destructive strength of the container-grown root balls. According to the approximated curve of against the CRBS for the ordinary condition of soil medium water content (ca.75％), 27％ or more CRBS is suggested to be a requirement for shipping in terms of securing minimum destructive strength with less than 6％ of RDSM.