We studied the pattern and causes of the habitat segregation of Fagus crenata and Quercus crispula on a snowy mountain in northern Japan. We established two study sites(“Forest site” and “Shrub site”)on the ridge of Mt. Hachiman in the Hakkoda mountain range, Aomori Prefecture, and we conducted forest census and measurements of environmental conditions. As a result, environmental conditions and the proportion of the two species differed between windward and leeward slopes for the winter seasonal wind: F. crenata was distributed in places with more snow and soil moisture, while Q. crispula in places with less. Path analysis was performed to estimate the causal relationship between the two species' density and environmental conditions. In the Forest site, located on a gentle ridge, the maximum snow depth and soil moisture, as well as slope inclination affected the two species' density. Moreover, the density of Q. crispula was estimated to be positively influenced by species other than F. crenata. In the Shrub site, located on a steep ridge, the same factors affected the two species' density, but the strength of the effect of slope inclination was greater than in the Forest site. These results suggest that differentiations in conditions of snow and soil moisture between the windward and leeward slopes are responsible for the local segregation of two species in snowy mountains, and that slope inclination also involves the local segregation in steep ridges. In addition, species other than F. crenata may have a positive effect on Q. crispula.

We examined the influence of drying on the germination of Abies mariesii seeds. The germination capacity of seeds stored at 4℃ and −20℃ was also observed. Germination experiments were conducted by adjusting the moisture content of the seeds to four levels (9.9, 7.1, 6.3％, and 5.1％). The germination rate did not decrease with drying intensity, and ＞70％ of seeds germinated in all treatments. The germination rate of seeds stored at 4℃ was ＜10％ after 3 years regardless of the drying treatment. For seeds stored at −20℃, the germination rate after 3 years ranged from 48.3％ to 77.4％. These results suggest that Abies mariesii seeds can be frozen and stored at a controlled moisture content, and that storage at subzero temperatures is effective in protecting the fruiting cycle.

The horizontal error of RTK-GNSS positioning and the effects of GNSS receiver settings on the error were tested under a forest canopy. The test was conducted in two public forests in Toyota City, Aichi Prefecture, Japan. The median of the horizontal error of RTK-GNSS positioning was about 0.878 m, and the maximum was about 4.011 m. The error of RTK-GNSS positioning was smaller than that of DGNSS. The GNSS receiver settings, such as the threshold of the signal-to-noise ratio (SNR) and occupation time, did not affect the horizontal error of RTK-GNSS positioning. Elevation mask under 25 degrees slightly decreased the error, but the maximum was over 4 m. To survey land boundaries in forests, a horizontal error within 0.9 m is needed; therefore, RTK-GNSS positioning may not be suitable for boundary surveys beneath forest canopies.

The correlation between crown length and mean increment in diameter at breast height (DBH) over a period of five years was investigated in five overcrowded, young and middle-aged Sugi (Cryptomeria japonica D. Don) stands. The threshold value of DBH, at which the mean DBH increment of Sugi trees is nearly zero, differed among the stands, whereas the threshold value of crown length, at which the mean DBH increment of Sugi trees is nearly zero, was 4.0 m in all stands. For the trees with a crown length over 4.0 m, the relationship between length index (with 4.0 m subtracted from the whole crown length) and mean DBH increment was analyzed using analysis of covariance (ANCOVA), and it was compared with the ANCOVA model with DBH as a covariate. The adjusted coefficient of determination of the latter model was significantly higher than that of the former model. With respect to the selection of thinned trees in overcrowded Sugi stands, it is reasonable to assume that trees with a crown length less than 4.0 m show little to no growth and that the greater the DBH, the more vigorous the growth of the trees with a crown length of over 4.0 m.

Under the Feed-in Tariff Scheme for Renewable Energy in Japan, the utilization of unused woody biomass was increasing because the government set a higher purchase price for renewable energy generation based on unused woody biomass. Moreover, the unused woody biomass included raw material made from thinning woods in the ratio of around 40％, so that effect of the increase or decrease in the utilization of woody biomass from timber thinning was not negligible. Thus, the purpose of this study was to simulate the changes in thinned timber production in 47 prefectures of Japan based on three scenarios considering the purchase period of 20 years under the Feed-in Tariff Scheme for Renewable Energy. The scenarios consisted of business as usual, thinning promotion and thinning decline, and the simulations calculated the commercial thinning volumes by prefectures in 2022 and 2032, starting at 2012. The results showed the common tendencies among prefectures were as follows: Thinned timber production was largest, in order, in the thinning promotion scenario, business as usual and thinning decline; thinned timber production increased in the thinning promotion scenario, decreased in the business as usual scenario and largely decreased in the thinning decline scenario from 2012 to 2032; Hokkaido, Shizuoka, Oita and Kagoshima Prefectures showed a large amount of thinned timber production and also had potential for a further increase in the future, so that these prefectures were particularly important in terms of meeting increasing demands for the utilization of unused woody biomass for renewable energy generation.

These researchers acquired the forest GIS for private and public forests from prefectures and national forests from the Forestry Agency of Japan. We then calculated incomes and expenditures such as silvicultural and harvesting as well as stumpage prices on the Japanese cedar, cypress, pine, and larch forests using the silvicultural prescription set based on the regional forest plans and operation system set based on topographic conditions such as slope angles and height differences with GIS. Finally, this study estimated the availability of unused materials for woody biomass power generation plants under operation with FIT at the end of June 2020 as the supply potential from the profitable subcompartments. As a result, supply potentials of used and unused materials were estimated at 65,490,336 m³/year and 13,098,067 m³/year, respectively whereas those availabilities were estimated at 31,080,672 m³/year and 6,216,134 m³/year respectively. Therefore, the rate of the availabilities to the supply potentials was 47.5％. Furthermore, the rate of the availabilities to the demands was 71.6％. Considering the subsidy rate of 100％ to secure the reforestations, the availabilities met the demands in Japan as a whole.

We investigated the process of log procurement by sawmills in Hokkaido after the operation of woody biomass power plants. We mailed a questionnaire to 137 sawmills July 2018, and received responses from 92 sawmills by August 2018. We analyzed responses from 84 companies that mainly processed Japanese larch (Larix kaempferi) and Sakhalin fir (Abies sachalinensis). As a result of our survey, approximately 80％ of sawmills in Hokkaido set their own procurement standards including criteria for crooked and decayed logs. The 68％ of mills that sawed mainly Sakhalin fir (Abies sachalinensis) and 40％ that sawed mainly Japanese larch (Larix leptolepis) replied that they felt it was difficult to procure logs that met specific quality requirements, such as girth and length. Approximately 70％ of the logs procured by sawmills were directly shipped from national and private forests. Furthermore, sorting was conducted by the log production entities. We conducted a telephonic survey of five woody biomass power plants regarding how they acquire unused wood for fuel. We found that 90％ of sawmills procured logs from areas within a 100-km radius, whereas power plants procured unused wood from places, such as satellite yards over a wide area up to 250 km away, revealing some overlap. Streamlining log sorting for these two purposes is considered to be challenging in the short term; however, it is important that the community finds ways for improvement.

The increase of wood use for biomass fuels in heat supply and power generation may change the yield rate, average price of the yield and costs of harvesting and transportation, thereby changing the profitability of forestry. In this study, we analyzed the effect of these changes on the annual supply and annual expense of the government for the subsidization. With a fixed maximal subsidy rate or fixed governmental expense for subsidy, an improvement of forestry profitability increases the annual supply as a result of an increase of stands that can be managed for wood production with the subsidy. The increase of yield rate causes a larger increase rate of annual supply because of both the direct increase of the yield and the improvement of the profitability. If the maximal subsidy rate is fixed, the governmental expense may increase due to the increase of subsidized stands. With a fixed annual yield, the improvement of the profitability reduces the governmental expense. In this case, the annual regeneration is also reduced with the improvement of profitability, because high-quality stands tend to be selected for subsidization.

The yield percentage by tree species was estimated and the effect on the amount of wood biomass resources available was examined. In order to estimate the yield percentage of larch, cypress, cedar, and red pine by species, the results of logging operations in Nagano Prefecture were used to determine the amount of timber cut and sold, and to estimate the yield of lumber produced. As a result, the yield percentage of all tree species in clear-cutting was lower than the conventional value, and in thinning, it was higher than the conventional value for all tree species except red pine. In addition, by yarding system, the value for vehicle-based yarding was higher than that for overhead wire-based yarding. Using these results, we estimated the amount of wood biomass resources available when the yield percentage was taken into account for each tree species and when the percentage was assumed to be constant as in the conventional method. The results showed that the availability of larch, cypress, and cedar increased, while that of red pine decreased, compared to the estimation by the conventional method. The results suggest that it is important to accurately estimate the yield percentage.

We developed a geographic information system (GIS) based simultaneous harvesting selection model, suitable for both coniferous and broadleaved stands, for supply of woody biomass to a power generation plant near Tosayama, Kochi City, Japan. The procedure was developed as follows: 1) the study region was divided into polygons representing watersheds, each of which represented a concave area suitable for harvesting using cable logging systems. 2) Those polygons adjacent to roads wider than 3 m were selected as suitable for log transportation by truck. Those polygons with a smaller area than the fixed logging area designated by the model were removed from the subject area. 3) After additional selection concerning conservation laws, tree species and stand age, the remaining polygons were analyzed for profitability per unit area. 4) The supply potential of both saw timber and fuel wood from the selected polygon area of 947 ha was estimated as 153×10³ m³ and 154×10³ t, respectively, each of which has a sufficient profit for regeneration.