A simple model that estimates the light environments within a strip clear-cutting stand was derived. The sky factor was used as a measure of light environment. In order to derive the model, we assumed that: 1) the direction of the strip was parallel to the incline; 2) the strip width and length were constant and infinite, respectively; 3) the inclination angle was constant; and 4) walls, the height of which was equal to the mean height of residual stands, were erected on both sides of the strip. Driving variables in the model included the strip width, height of residual stands, position within the strip and inclination angle. In six strip clear-cutting stands, the sky factor estimated by the model was compared with that measured with hemispherical photography. In four of the six stands, there was no significant difference between estimated and measured sky factor. However, the sky factor in the other two stands was underestimated, since the model assumed that no light penetrated into the strip through the canopy of residual stands. Model simulation demonstrated that the inclination angle should be taken into account when estimating light environment in strip clear-cutting stands. The model presented here provides a simple means for estimating light environments in a strip clear-cutting stand, and thus it will be beneficial as a tool for developing a guideline for the strip clear-cutting.

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To evaluate the effect of volcanic ash deposits and pine wilt disease on Pinus densiflora mortality in the Kirishima Mountains one year after the 2011 Shinmoe-dake eruption, we investigated the mortality rate in 84 P. densiflora forest stands and measured the depth of volcanic ash deposits from the 2011 eruption in those stands and around 117 dead P. densiflora trees which were examined for the presence of Bursaphelenchus xylophilus. Although mortality rate was less than 20% in stands with volcanic ash depths shallower than 20 cm, it ranged from 60 to 100% in three stands along a hiking trail located at altitudes above 1,000 m where the volcanic ash stood depths were deeper than 25 cm. B. xylophilus was not detected in any dead P. densiflora tree sampled along the hiking trail, but was found in 86 dead trees below c.a. 950 m where the volcanic ash deposits were shallow. This evidence indicated that heavy volcanic ash deposits might cause extensive damage to P. densiflora without pine wilt disease. But some dead P. densiflora trees infected by pine wilt disease were found around the damaged P. densiflora forests where the forest floor was covered by a deep layer of volcanic ash. The results suggested the importance of controlling pine wilt disease in the region to preserve the surviving P. densiflora trees as a seed source for natural regeneration of P. densiflora forests damaged by the 2011 Shinmoe-dake eruption.

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Evaluation of the impact of deer on natural forests requires a method that considers a variety of damage forms such as bark-stripping and browsing. Many individuals should be involved in the evaluation on a regional scale, and the method should be simple and objective. We conducted a survey using a simple check list of browsing scars and traces of deer. The check lists were completed by foresters of the district forest office, and 1,371 records were used for the analyses. The results of a multiple correspondence analysis (MCA) for 10 items suggested that each site could be plotted on a coordinate with three directions indicating that the impact was high, low, or unknown. The primary factors in the scoring of sites were correlated with sightings per unit effort (SPUE) by hunters. Many answers by foresters included the “Unknown” category for the existence of browsing scars and the abundance of less palatable plants. The number of replies where browsing scars were detected was lower for check lists completed by foresters than for those by the authors at the same sites, suggesting the under-recording by foresters. Estimation of the impact levels of deer on natural forests in Hokkaido by kriging the primary factor of MCA at each site was considered a valid technique, compared with existing information.

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To clarify radiocaesium migration with litterfall from the tree canopy to the forest floor, a study was conducted in the three different forests in Fukushima Prefecture where radionuclides released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) were deposited. Concentrations of ¹³⁴Cs and ¹³⁷Cs in the litterfall had been periodically monitored for 11 months since four months after the accident and were analyzed. The concentrations in the litter samples were generally higher in the cedar forests than those in the hardwood-Japanese red pine mixed forest; because the hardwood trees had no leaves at the time of the accident, most of the resuspended radiocaesium is considered to have been deposited on the forest floor through canopies. Meanwhile, the cumulative deposition of radiocaesium in the cedar forests was found to be higher than that in the hardwood-Japanese red pine mixed forest. This confirmed that large amount of radiocaesium still remains in the tree canopies. Although not many differences were observed in the radiocaesium concentrations in the litterfall since October 2011 in any forest stand, radiocaesium deposition remarkably increased due to a large amount of litterfall from the canopies. Together with the litterfall, vertical distribution of fresh leaves in the canopies, horizontal distribution of litter on the forest floor, throughfall, and stemflow should be monitored to clarify the comprehensive migration of radiocaesium in the future.

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We report details of a fatal accident in Ogaki, Gifu Prefecture, involving a first-grade girl who was hit directly on the head by a falling tree branch (length 3.5 m; weight 5.4 kg) while participating in a forestry experience program. The branch, from a large Cryptomeria japonica tree, was viable but had many galls, and it fell from a height of 23 m after being broken off by a strong gust of wind (maximum wind speed ca. 10 m/s). The artificial forest where the accident occurred is an isolated one composed of C. japonica and Chamaecyparis obtusa trees, where 68% of the C. japonica trees in the large size class (> DBH 40 cm) are affected by gall disease. The mean density of fallen branches longer than 1.5 m on the forest floor was recorded as 207/ha, and all had fallen within a distance of 5 m from the large trees with gall disease. When a strong wind is blowing, it is considered very dangerous to stay under large C. japonica trees, because any large branch that breaks off from a high point may fall down through the other branches with its broken part directed downwards. This incident underlines the need to pay more attention to the danger of falling branches in areas where trees have gall disease.

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Asiatic black bears (Ursus thibetanus) have been stripping the bark of Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) at increasing rates in forest plantations across Japan. This has become a serious issue affecting the forest industry and local communities. In response, effective damage control methods need to be developed based on the best available science. We reviewed the Black Bear Spring Supplemental Feeding Program (SFP) developed by the Washington Forest Protection Association’s Animal Damage Control Program (ADCP) and analyzed the applicability of the program to the Asiatic black bear problem in Japan. From the several causes of the stripping the bark damage by bears, we argue the supplemental feeding program designed in Washington State would be effective in Japan. However, we caution that before conducting a local feeding program, we should address several topics, including: (1) conduct experimental studies to cross-investigate bark stripping mechanisms; (2) discuss the pros and cons of artificially feeding wildlife; and (3) identify how to prevent arbitrary feeding by unauthorized entities.

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