In order to make a projection of the future of forestry in Japan in a society with declining population, the future demand and supply of timber, the number of forest workers and required labor were estimated. Forest workers are expected to decrease to 70% of the current number by 2030 and 50% by 2050, as per the cohort-change rate method. Potential demand for domestic timber is expected to be 34 million m3 in 2020's. Using forest resource and forestry statistics, data necessary for future estimation were calculated. The wood supply amount and the required labor amount were estimated up to 2029.The wood supply amount estimated by the felling area rate and planted forest area by age class will be lower than the potential demand, and the required labor amount slightly will exceed the estimated number of workers. When raising the harvested area rate by 1.5 times so that the amount of wood supply could meet the demand, the required labor amount will exceed the number of workers by 10% even if the silvicultural work was saved. It was calculated that it is necessary to increase the number of workers by raising the entry rate of young people, or to accelerate the harvest productivity improvement, or to improve timpber utilization rate in order to lessen the labor supply-demand gap. It should be noted that these estimation results were obtained by accumulating various assumptions. Although the share of silvicultural work in the required labor amount is expected to increase, it is expected that the required labor amount for silviculture will remain at the current level if the labor saving of 1% per year continues after the shift to labor-saving silvicultural work.

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We examined growth performance of planted trees in the last 16 years in the multi-storied Japanese cedar (Cryptomeria japonica) plantations with the upper story trees being over 100 years old and the mid and lower story trees being 30 to 52 years in Kuma district, Ehime prefecture, Shikoku, Japan, to clarify if planted trees can grow soundly in the old-aged multi-storied conifer plantation under intensive forest management. The diameter growth rate showed more than 0.80 cm/year for the upper- and mid-story trees, which was similar or higher than that of trees in a single-storied plantation. It was 0.25 cm/year for the lower-story trees, which was lower than that of trees for the upper- and mid-story trees. The height growth rate showed more than 0.5 m/year for the mid-story trees. However, it appeared to reach a plateau for the upper story trees, 0.13 m/year, for the upper-story trees and 0.22 m/year for the lower-story trees. The height/diameter ratio was lower than about 60 for the upper story trees, whereas it was from 70 to 120 for the mid-story trees. Median height/diameter ratio showed over 100 in the lower-story trees. This multi-storied plantation can be mentioned as a rare example of good practice in terms of its high growth rate in terms of upper- and mid-story trees, owing to a long-term intensive tree density management by the owner. However, the high values of height/diameter ratio for a part of the mid-trees and most of the lower-story trees and low growth performance of the lower-story trees suggest high risk of snow accretion damage and the difficulty of maintaining the multi-storied plantation sound for a long time even under intensive forest management.

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We characterized the soil properties of black truffle (Tuber himalayense) and white truffle (T. japonicum) growth sites in Japan, necessary for establishing artificial cultivation techniques. At five T. himalayense and four T. japonicum sites, we collected surface soils (0–5 and 0–15 cm depths) at five points from adjacent plots with or without ascocarps. We evaluated soil chemical properties, soil texture, and soil microbial biomass carbon and nitrogen. Soil chemical properties and microbial biomass carbon and nitrogen at 0–5 cm did not differ between plots with and without ascocarps. Soil textures were diverse among sites for each Tuber species, and similar to those reported for other Asian and European Tuber species. In T. himalayense sites, there were no significant differences between plots with and without ascocarps in soil chemical properties at 0–15 cm. However, in T. japonicum sites, exchangeable calcium and the sum of exchangeable cations at 0–15 cm were significantly lower in plots with ascocarps than in plots without ascocarps. T. japonicum may be adapted to more acidic soil (pH 5–6) with poor nutrient concentrations. T. himalayense habitats are characterized by weakly acidic to alkaline soils (pH 6–8) with a relatively high base saturation ratio.

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The aim of this study was to compare between different load capacity forwarders in the productivity of longer log production and to clarify longer log productivity and the effect of the forwarder’s loading capacity or platform dimension on productivity. We surveyed the following activities: loading to forwarder with a grapple loader or harvester, forwarding with 6 ton load capacity as large forwarder and 4.8 ton as middle, and unloading from forwarder with grapple loader. The produced log length classes were 6 and 8 m as longer logs and 4 m as regular length logs. The productivity with the large forwarder was slightly higher than that with the middle in loading and unloading, even considering the difference in log volume, probably owing to the improvement in workability because of the broader platform of the large forwarder. Considering the driving speed in forwarding with two newly defined indices, the greater the log length, the smaller was the velocity ratio when compared with the same loading ratio. The former index is the ratio of forwarding speed in loading to that in unloading and the latter is the ratio of loading volume in each cycle to that of the maximum of the machine used. The cause of this reduction in speed was presumed to be because of the shift in the center of gravity and the resultant instability of the forwarder. The total productivity of loading, unloading, and forwarding was the highest in the case of production of 4 m logs with both the large and middle forwarders. However, the rate of reduction in productivity owing to the longer log was lower with the large than with the middle forwarder. Hence, it was confirmed that large forwarders are more suitable for longer log production.

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The purpose of this study was to determine the size effect parameter for the design strength that corresponds to the Japanese Agricultural Standard for lumber. This was performed using an existing database that contains lumber strength properties. Initially, each size effect parameter for the constant span, specimen depth, and span/specimen depth ratio of the E70 grade sugi (Japanese cedar) was obtained using its bending strength, and each size effect parameter was confirmed to agree with the values reported in previous studies. Then, the size effect factor was considered with an objective to reduce the design strength based on the specimen depth. The bending strengths of sugi, akamatsu (Japanese red pine), and Douglas fir were adjusted to the values under the standard loading conditions using an existing adjustment formula. In addition, the 5% lower limit of the bending strength was obtained for each species, grade, and specimen depth. The ratio of the 5% lower limit of bending strength and the design strength corresponding to the Japanese Agricultural Standard for lumber (5% lower limit/design strength) was calculated and compared with the size adjustment factor for the standard specimen depth of 150 mm. Thus, under the standard loading conditions, it was inferred that the value of the size effect parameter for the size adjustment factor was approximately 0.4–0.5.

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We aimed to estimate the amount of radiocesium re-dispersed by sugi (Cryptomeria japonica var. japonica) pollen release accurately based on measurements of sugi male flowers before pollen release. We measured the biomass and cesium-137 (¹³⁷Cs) concentrations in male flowers and sugi pollen in November (shortly after pollen maturity), and in the following February (shortly before pollen release), in forests impacted by the 2011 Fukushima Daiichi Nuclear Power Station accident. Pollen accounted for ca. 1/3 of male flower biomass and the ¹³⁷Cs concentrations were not significantly different between male flowers and pollen in November in the Koriyama sugi forest. The regression relationship between male flower and pollen 137Cs concentrations was used to calculate pollen ¹³⁷Cs concentrations for every November–December period in the years 2011–2015 at 21 localities in Fukushima Prefecture. The sugi pollen ¹³⁷Cs concentration declined year on year. The concentration in the spring of 2016 was ca. 8% of the concentration in spring 2012. The calculated ¹³⁷Cs T_ag (aggregated transfer factor) for the transmission of ¹³⁷Cs from the environment to pollen was 0.0203 m² dry kg^–1 in February 2012 and 0.00168 m² dry kg^–1 in February 2016, based on data available in the MEXT ¹³⁷Cs deposition quantity distribution map.

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To detect species dependent on old-growth evergreen broad-leaved forests and compare assemblages between old-growth and other forest environments, silphid and dung beetles were collected with using carrion baited pitfall traps in old-growths, middle-aged conifer plantations, middle-aged secondary forests, young secondary forests and open lands in the Aya district, Miyazaki Prefecture. Species richness and diversity index were higher in plantations and middle-aged secondary forests than in the old-growths. No old-growth dependent beetle species were found and beetle assemblages were not different among sites in the old-growths, middle-aged conifer plantations, and middle-aged secondary forests. Many species were forest generalists found in several forest types but Nicrophorus concolor, Ptmascops morio, and Onthophagus fodiens were significant indicators of the middle-aged secondary forests. On the other hand, Onthophagus nitidus was abundant especially in the open lands and the young secondary forests. These collectively made up the beetle assemblages in the open lands and the young secondary forests different from the old-growths, the plantations, and the middle-aged secondary forests.

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