Planted Quercus serrata seedlings in oak forests, previously affected by Japanese oak wilt or subject to retention harvesting, experience diverse light conditions due to the presence of retention trees. To elucidate the effects of differences in light environment on the growth of planted Q. serrata, a survey was conducted five years after planting across 22 plantations (3 clearcut and 19 retention harvesting sites) in Toyama Prefecture, Japan. Two study plots were established at each plantation, with weeding conducted annually. Diffuse transmittance (DT) across plots varied widely from 5％ to 94％, corresponding to the amount of retention trees. Reduction in planted tree height due to die-back occurred frequently in dark environments. Based on the model equation, tree height growth was impeded at DT below 24％, and survival rates decreased to less than 66.6％ at DT below 16％, thus rendering such dark environments unsuitable for planting. Tree height was greater in brighter environments, whereas survival rates were higher in medium-light environments with approximately 50％ DT. A thorough investigation of the four plots revealed that brighter environments caused more abundant competing vegetation and higher accidental cutting ratio (up to 50％), suggesting that these were factors for decline in survival rates in bright environments. In medium-light environments, tree height growth was slow, but survival rate remained heigh; therefore, artificial regeneration of Q. serrata will likely be successful.

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.

This study reports the results of a student survey from FY 2018 to FY 2022 for forestry colleges in Shizuoka， Nagano, Kyoto, and Shimane Prefectures. We clarified the overall trends and characteristics of student attributes，and discuss the future of forestry colleges. Overall colleges, about 90％ of students were male and mainly in their twenties. Most guardians were not engaged in forestry, and families did not own forests. The students graduated from high school general course and knew about the college through their family or teachers. The following characteristics were observed in each college. Shizuoka were in twenties within the prefecture. They knew the college through their teachers. Nagano had a higher percentage of women and those from outside the prefectures. Kyoto had a small number of students in their forties and fifties that it have not seen in other colleges were also found. A high percentage of the students were from other prefectures and had a working experience. They got the college information from the Internet. Shimane were mainly males within the prefecture and high school graduate. As described above, common trends were observed among the colleges, as well as the characteristics of each college. Based on the above, it is important for forestry colleges to conduct student recruitment and educational activities that match the trends and characteristics of students. In addition, forestry colleges are expected to evolve as comprehensive human resource development base for the forestry industry.

Increase in Cryptomeria japonica harvesting is expected to result in a shortage of rooted cuttings. To increase rooted cutting production, it is crucial to increase the number of scions per ortet and shorten the growth period of rooted cuttings. As the number of harvested scions can be expected to increase by shortening the length of the cutting, this study aimed to examine whether it is feasible to grow container-rooted cuttings from short cuttings in 1 year. Approximately 10-30-cm-long cuttings were inserted into kanuma soil and transplanted into containers filled with fertilized medium immediately after rooting. Subsequently, the relationship between cutting length and containerized rooted cutting height after one growing season was investigated. The cuttings started to root in mid-March or earlier upon heating from below in an electrically heating bed, and otherwise in late April. Results of a linear mixed model showed that, the longer and earlier the rooting cuttings grew, the larger the rooted cuttings were. The analysis of the relationship between rooted cutting height and growth period, estimated from the transplantation date, suggested that transplantation was necessary by mid-May for 10-cm-long cuttings and by late June for 15-cm-long cuttings to obtain containerized rooted cuttings with an average height of 30 cm. As 10-15-cm-long cuttings are shorter than normal and are expected to yield more cuttings, the method presented in this study will contribute in increasing rooted cutting production.

The landslides (tephra slides) caused by the 2018 Hokkaido Eastern Iburi Earthquake gave rise to many bare slopes. In order to verify forest regeneration through Japanese larch (Larix kaempferi) planting, three test sites were set up on the bare slopes. At test sites Takaoka B and Horonai, where clayey tephra was observed in the topsoil, the soil had lower permeability and was harder than Takaoka A, where a large quantity of residual tephra was present. The low water permeability and hardness were moderate in Takaoka B and severely poor in Horonai. In the third year after Japanese larch was planted in each test site, Takaoka B larch had a significantly smaller tree height, diameter, and height growth than those of Takaoka A. At the same time point, Horonai larch had a significantly smaller tree height, diameter, growth amount, and growth rate than those of Takaoka B. These results indicate that, on bare slopes caused by landslides, firstly, the low water permeability and hardness of clayey tephra are the primary factors that inhibit the initial growth of planted Japanese larch, and secondly, the lower the permeability and harder of clayey tephra, the smaller the initial growth of planted Japanese larch trees.

Bamboos (Poaceae; Bambusoideae) typically exhibit a unique pattern of mass-flowering and one-time fruiting after long-term clonal growth. This phenomenon leads to a collective die-off and significant changes in the vegetation of the area, but the condition of the bamboo stand in this process has been overlooked. In this study, we investigated a method for the classification of various states of bamboo stands from flowering to the subsequent decline and death processes. Focusing on the condition of bamboo ramets within flowering bamboo stands, we proposed a classification into 11 stages based on literature review and our field observations. These stages are broadly divided into four categories: non-flowering, flowering and fruiting, post-flowering decline, and death. In the bamboo garden of Kyoto University, we applied this classification method to bamboo plantations consisting of three genera, four species, and two forms that flowered from 2017 to 2022. This allowed us to confirm that it is possible to quantitatively assess not only the condition of the stand at the time of flowering but also the stages from decline to death. Additionally, we clarified that the process from flowering to death at stand level takes more than one year.