This study was conducted in a watershed (357 ha) where landslides occurred after the Hokkaido Eastern Iburi earthquake (M_w 6.6) on September 6, 2018. To assess the occurrence of landslides and their impact on carbon stocks, we examined the amount of aboveground and belowground carbon stocks in different forest types to estimate watershed-scale carbon stocks affected by earthquake-induced landslides. Estimated watershed carbon stocks were 6×10⁴ t-C aboveground and 13×10⁴ t-C belowground. GIS analysis identified 428 landslides with a total landslide area of 74 ha and a landslide area ratio of 20.6％. On the other hand, landslide area ratios differed among forest types, with the highest ratio of 31.7％ in old deciduous forests (81 years and older), followed by 39-45 years old larch forests with 29.3％. Alternating layers of volcanic deposits (tephra) and andisol soils were observed to a depth of 2-3 m, with high carbon accumulation in the andisol and associated loam layers. The carbon stock affected by landslides was estimated to be 4×10⁴ t-C, assuming an average failure plane depth of 1.5 m. The carbon stock in the older forest was high, and consequently the carbon runoff from landslides was also high. The amount of carbon runoff in the study watershed was 21.7％ of the total carbon stock, which tended to be high compared to the ratio of landslide area. Due to widespread landslides, changes in the above- and below-ground forest conditions induce long-term effects on carbon stocks as a forest ecosystem service.

A synthetic cytokinin of N⁶-benzylaminopurine (BAP) can induce female strobili in clusters of male strobili in Japanese black pine. In order to use the hormonal method of BAP to improve seed production in seed orchards in cold regions, we investigated effects of BAP treatments (paste application on winter buds, injection of solution into branches and stems), the timing of treatments (5, 13, 20, 27 September, and 4 October 2013), and the clones (five clones) on female strobilus induction in a seed orchard in Aomori Prefecture, measured the time required for each treatment, and estimated the yields of seed and seedling produced by the best of the treatments. All types of BAP treatment induced female strobili in clusters of male strobili, although their effects varied by type (higher for branch injection and lower for stem injection than paste application, P＜0.05), timing (more effective from mid to late September than earlier and later, P＜0.001), and clone. Stem injection needed the shortest time and the time required for the others was comparable. The percentage of seeds filled and the germination rate of seeds in corns induced by BAP treatment were approximately 65％ of normal seeds. Branch injection, which could most effectively enhance female strobilus induction, would increase 3.8 corns producing 40 seedlings per cluster of male strobili. In a tree, 5 primary branches given the injection could produce 5.8 times as many seedlings as an untreated tree in the seed orchard.

This study examined the spatial structure of vegetation in the sprawled Satoyama woodlands, which is thought to have been shaped by past land-uses. During the mid-20th century, the upper slopes of the hillside surrounding arable land in the surveyed area were covered with naturally grown forests. Conversely, the lower slopes bordering the arable land were characterized by low vegetation that is thought to be grasses or brushes. According to residents, in the mid-20th century, forests on the upper slopes were harvested for firewood and charcoal production every 10 years or more, whereas grasslands on the lower slopes were managed as meadows and mowed multiple times every year. Differences were observed in the present-day woodland's species composition between sites previously occupied by naturally grown forests and those covered with grasses or shrubs in proximity to arable land. Notably, Quercus serrata, which overwhelmingly dominates the former sites, was entirely absent in the latter. Q. serrata is believed to have maintained natural populations in coppices, grasslands, and brushlands owing to its proficient sprouting and precocious reproduction. However, instances of exceedingly frequent disturbance (occurring multiple times annually) by mowing likely inhibited Q, serrata from sprouting, seed regeneration, and, ultimately, population establishment. Thus, the vegetation in the sprawled Satoyama woodlands had an inhomogeneous spatial structure reflecting the effects of past land use.

The prediction of yield plays a crucial role in sustainable forest management practices. Competition indices have been widely adapted for individual-level yield growth models, and many studies examined the effectiveness of distance-dependent model and distance-independent model. In Japan, previous studies evaluated the efficacy of both models specifically for Japanese cedar (Cryptomeria japonica) trees and showed that the distance-independent model had the same accuracy as distance-dependent model. However, studies that have applied these indices for Japanese cypress (Chamaecyparis obtusa) trees are scarce. This study evaluated the prediction accuracies for the four distance-dependent competition indices and five distance-independent competition indices for an individual-level diameter model of Japanese cypress trees across varying thinning intensities within the Shikoku region. Additionally, the effectiveness of this model as a yield prediction technique were discussed. The findings suggest that the MD (Mean distance) and BR (Basal area ratio) had high interpretability for the diameter model of Japanese cypress trees, with distance-independent competition indices exhibiting higher interpretability than distance-dependent competition indices. Moreover, the distance-independent competition indices demonstrated satisfactory accuracy and efficiency for the diameter growth model of Japanese cypress across various thinning intensities, thereby supporting yield prediction.