Japanese black pine (Pinus thunbergii) is tolerant against salty wind but susceptible to pinewood nematodes, whereas Japanese red pine (Pinus densiflora) is more resistant against pinewood nematodes than P. thunbergii but weaker against salty wind. To produce materials with high resistance against pinewood nematodes and high tolerance against salty wind, we focused on seedlings derived from putative hybrid clones (Pinus × densi-thunbergii). In this study, we investigated the nuclear DNA genome composition of two putative hybrid clones. Using a PCR-RFLP method for analyzing chloroplast DNA, we subsequently identified the paternal species of progenies of two putative hybrids. Branches and potted seedlings from the progenies of P. densiflora, P. thunbergii, and the hybrids were immersed in seawater. We harvested the needles from them and measured the potential maximal PS Ⅱ quantum yield (F_v/F_m). We also dried some needle samples and used inductively coupled plasma mass spectrometry (ICP-MS) to determine Na concentrations. Nuclear DNA analysis of the putative hybrid clones revealed that they were F1 hybrids (P. × densi-thunbergii). Chloroplast DNA analysis revealed that progenies of the hybrid clones were sired by P. densiflora. Those progenies were significantly more salt tolerant than P. densiflora. Moreover, the Na concentration of needles of hybrid clones was lower than those of P. densiflora. Our results suggest that the progenies of hybrids are potential candidates for plantation in coastal pine forests, due to high resistance against pinewood-nematode and high tolerance against salt water.

Mass mortality caused by bark beetles occurred locally in a subalpine fir (Abies mariesii) forest in the Zao mountain area in northern Japan. We examined the distribution of the mass mortality of A. mariesii trees and the corresponding locations to analyze the mortality rate in each section of a 50 m mesh, using satellite images and GIS, in a 528 ha fir forest in Yamagata Prefecture. Our results show that there were three areas where sections with mortality rates of 60％ or more were concentrated in this study area. They were located on western slopes with high altitude. However, since there were still many sections with low mortality rates in these locations, the local occurrence of mass mortality could not be explained by location alone. Sasa bamboo (Sasa kurilensis) dominates the forest floor in many fir forests. Study plots with higher sasa coverage had fewer juvenile A. mariesii trees. Sasa coverage tended to increase as altitude increased, and there were no A. mariesii seedlings and saplings in the plots at high altitudes. This tendency was extremely noticeable on the western slope of Mt. Jizoudake, which was also the area in which sections with high mortality rates were most concentrated in this study area. Therefore, mass mortality forests dominated by sasa at high elevations are predicted to be difficult to regenerate because they have few juvenile trees on the forest floor.

To identify conditions for coppicing and to regenerate old and large-sized Quercus serrata stands, we investigated both environmental factors (such as altitude and slope) and stump conditions (such as cutting age, stump diameter, stump height, and number of trunks per stump) from 12-years old to 76-years-old stands. We used a generalized linear mixed model (GLMM) to evaluate the effects of environmental factors and stump conditions on the probability of sprouting, number of shoots per stump, and the maximum height and the maximum diameter of shoot per stump. As cutting age increased, the probability of sprouting decreased: 68, 46, and 32％ in 40-, 50-, and 60-years old stands, respectively. The number of shoots per stump was positively affected by the number of trunks per stump and stump height. Both the maximum height and the maximum diameter of shoot per stump were also positively influenced by the number of trunks per stump but negatively influenced by cutting age. This study suggests that it is difficult to regenerate old and large-sized Q. serrata stands (more than 60-years old) by coppicing. However, there is a possibility of regenerating stands that are 40-50 years old by coppicing, if stem conditions are suitable. Our data also indicate that the number of trunks per stump may be a good indicator for considering the possibility of regeneration success.

With the introduction of high-performance forestry machinery, the repair and purchase costs for the machinery form a high proportion of the overall management costs. To understand mechanisms to increase the operating rate of machinery and reduce costs, we investigated the machine repair and renewal strategies of logging contractors. Seven mechanized logging contractors in Miyazaki Prefecture, Japan, were interviewed. To reduce repair costs, it is important to reduce the frequency of repair work, to use machines whose operating time is short, and to operate machines carefully. For these strategies, minor repairs are carried out by the contractors themselves. Some contractors use insurance attaching leasing machine. Large-scale machinery contractors have established a machine renewal system, with regular self-financed renewal of equipment. For smaller contractors with fewer machines, the use of subsidies and machine rental was possible, but subsidy use is subject to restrictions on second-hand sale, and rental is unsuitable for long-term use. Both extending machine working life and establishing a renewal system for machines are highly important for the stable management of mechanized logging contractors.

The year 2019 marked the first year of introducing the national forest environment transfer tax. The forest environment transfer tax scheme is mainly for the forest management in municipalities. Yet the forest areas in certain urban areas are limited and there is a room for urban-rural collaboration. In concrete terms, urban municipalities can receive relatively large revenue from the tax, because total population of municipalities is considered as one of the indicators to compute the amount of transferred tax for the municipalities. The urban municipalities can use the tax to facilitate the use of wood products, such as construction materials, and to conduct forest management in rural municipalities by implementing urban-rural collaboration. As a case of the urban-rural collaboration, collaboration between Toshima District and Chichibu City was analyzed and their process of collaboration and status of sharing human resources in Chichibu City and Saitama Prefecture were identified. Toshima District and Chichibu City have long-term experience of collaboration as sister municipalities. Chichibu City is conducting regional collaboration with surrounding municipalities on forest managements. These are the contexts of facilitating Toshima and Chichibu's urban-rural collaboration.

An important problem of the forest inventory using the terrestrial laser scanning (TLS) is the undermeasured tree height. To resolve this problem, we improved Pressler method, which is originally proposed for estimating stem volume, as follows: the diameter at breast height is reduced by a certain ratio, and then the height above ground level at the position of the reduced diameter is defined as the critical height. The relationship between critical height and tree height is also formulated in advance using data on stem form of felling trees. Then, inserting the critical height measured with TLS enables us to estimate the tree height. Using felling tree data of four coniferous species (Japanese cedar, Japanese cypress, Japanese larch and Jack pine), the relationship between critical height and tree height was analyzed, and the applicability of the improved method was evaluated. The results demonstrated that the underestimation of the tree height can be reduced if the critical height can be measured with TLS.