Nationwide standards about sawn lumber and allowable stresses have improved since the Meiji era in Japan. These
standards and allowable stresses were inherited through a large number of establishments and amendments. However,
the background and basis of values in many standards and allowable stresses remain unclear or unknown. This paper
aims to discuss the history and basis of sawn lumber standards and allowable stresses in Japan.
Short-rotation harvesting of Salix species has been studied for potential biomass resources because of their great bud flush. The chemical characteristics and extractability of bark extractives, especially condensed tannin, from 1-2- and 3-5-year-old Salix pet-susu and Salix sachalinensis trees were investigated. Among the results, the yields of 70% acetone aqueous extractives from the bark of S. pet-susu and S. sachalinensis were 29.0% and 25.8% (based on oven dried bark), respectively; and the tannin polymer contents of the extractives of S. pet-susu and S. sachalinensis were 43.4% and 39.4% (based on 70% acetone aqueous extractives), respectively. The chemical characteristics of the tannin polymers were determined by 13C-NMR, Py-GC/MS, and GPC analyses, and the tannins of S. pet-susu and S. sachalinensis consisted mainly of procyanidin and prodelphinidin. The approximate degree of polymerization was calculated as 6 (S. pet-susu) and 5 (S. sachalinensis). From the results of total extractives with water extraction at various temperatures, and with organic solvent extraction, the highest yields of total extractives and total polyphenols were obtained with 100 °C water extraction. On the other hand, those of total flavanols were observed with 70% acetone extraction. In order to consider an alternative treatment for debarking and grinding treatment, crush treatment was conducted, and the results indicated that such treatment raised the yields of total extractives, total polyphenols, and total flavanols to those from powder form. Additionally, it is evident that a 2-hour extraction time was the most effective to obtain condensed tannin from the crushed sample of S. sachalinensis and a 1-hour extraction time was adequate in the case of S. pet-susu. Based on the results, we conclude that short-rotation harvested Salix trees are potentially valuable natural resources for useful chemicals, especially condensed tannin.
Exponential smoothing (ETS) method and autoregressive integrated moving average (ARIMA) models have been
applied to forecasting monthly price of logs, sugi (Japanese cedar, Cryptomeria japonica D. Don) and hinoki (Japanese cypress, Chamaecyparis obtusa (Sieb. et Zucc.) Endl.). In this research, we evaluated the forecast accuracy of these two approaches through cross validation. Monthly current price data from January 2002 to December 2016 were used. The results show that the forecast accuracy of ARIMA models was not statistically significantly different from that of ETS method at 5% level for the period from January 2010 to December 2016 under all 12 forecast horizons of one month to 12 months. By comparing with the amount of changes in original prices, it was found that both ETS method and ARIMA models forecasted with smaller mean absolute errors than mean absolute amount of changes in prices within 8 months of forecast horizons at 5% level, which showing that ETS method and ARIMA models outperformed naive method. However, by comparing with seasonally adjusted naive method, ARIMA model showed better forecast accuracy only for forecast horizons of 1 and 2 months for hinoki at 5% level of statistical significance, while ARIMA model at other horizons and ETS method did not outperform seasonally adjusted naive method in forecast accuracy.
The effects of thinning on canopy interception loss, evapotranspiration, and runoff were investigated by a paired
catchment experiment in a small headwater catchment in Japan. A 0.88-ha catchment covered with a Chamaecyparis obtusa plantation that was planted in 1986 was intensively thinned in March 2009 following a 3-year calibration period (2006-2008). To avoid disturbing the soil surface, thinning was conducted by forest workers using chainsaws, and the thinned trees were left on the forest floor where they fell. Thinning removed 50 % of the trees, 30 % of the timber volume, and 22.5 % of the basal area. Canopy interception loss decreased by 4 % in the first year after thinning, and it returned gradually to the pre-thinning level for 3 years. The maximum increase in the annual runoff, 147 mm, occurred in the second year after thinning. The mean annual increase in the runoff during the post-thinning period (2010-2012) was 54 mm, although this was not statistically significant. The mean annual evapotranspiration significantly reduced by 140 mm, and the reduction was especially large during the growing season. In conclusion, it seemed that the intensive thinning in a small headwater plantation was effective to increase net precipitation and stream water for a short period.
Most of the combustion ash produced from the woody biomass power plant has been considered as industrial waste. However, ash contains nutrients such as Ca and K and may be reusable as a fertilizer and/or soil material for cultivating seedlings. To evaluate the feasibility of using ash as container growing media, we measured the growth and nutrient status of Sugi (Cryptomeria japonica) and Hinoki (Chamaecyparis obtusa) seedlings planted in containers with different mixing ratios of 0% (as a control), 5%, 10% or 25% of ash application (by volume). Ash application did not increase the seedling size of both Sugi and Hinoki. The height, diameter, and biomass growth of Sugi treated with 25% ash application were significantly restricted compared with those of other treatments. In Hinoki, the height, diameter, and biomass growth were significantly restricted with 10% and 25% ash application. The exchangeable Mg and Na contents in the growing media at the end of the growing season were lower in the seedlings treated with a higher ash mixing ratio. Needle Ca content of Sugi was increased with a higher ash mixing ratio, whereas that of Hinoki was comparable among treatments. No significant difference was observed in needle Mg and K contents of both Sugi and Hinoki among treatments. These results suggested that ash could be mixed up to 10% and 5% for Sugi and Hinoki, respectively, into container growing media without restricting seedling growth. It would be necessary to investigate whether ash-mixed seedlings grow well after planting in a forest.
The stand dynamics of a natural coniferous forest during 60 years after severe wind damage in 1954 was examined in the Higashitaisetsu area, central Hokkaido. This stand had a standing tree density of 1,230 trees/ha, a basal area of 46.15 m2/ha, and a stand volume of 423.4 m3/ha in 2014, 60 years after the wind damage. The stand volume was 1.8 times greater than before the wind damage. The number of trees increased in the first 37 years after the wind damage, probably largely due to the growth of advance regeneration; however, subsequently the number of trees began to decrease, probably due to the competition among trees and the decrease in ingrowth rate. Based on a stand development stage after a replacing disturbance, we considered that the forest stand was the stand initiation stage about 40 years after the wind damage and then moved to the stem exclusion stage.
Retention forestry, a part of silvicultural system that retains important forest structures and organisms at harvest time, is a promising way to conserve biodiversity in managed forests. This harvesting method is being widely adopted
in many countries and tested in field experiments. A large number of conifer plantations in Japan are reaching the planned harvest age, and their harvest is expected to help meet the domestic demand for wood. On the other hand, the restoration of conifer plantations to natural broad-leaved forests and the maintenance and enhancement of ecosystem services other than wood production are required in plantation landscapes. In this context, we launched a large-scale retention forestry experiment (the REFRESH project) in Sakhalin fir (Abies sachalinensis) plantations in central Hokkaido, northern Japan. The REFRESH project has six treatments (clear-cutting, three levels of dispersed retention, aggregated retention with a 0.36 ha intact patch, and gap cutting) and two controls (unharvested natural forest and unharvested plantation) with three replicates each. In dispersed retention, naturally regenerated broad-leaved trees are retained at three levels to maintain and restore elements of natural forests. After harvesting, fir seedlings are planted in the harvested area. We conducted pre- and post-harvest surveys on water and soil conservation; forestry efficiency; and the diversity of plants, arthropods, and birds. The initial surveys indicate how tree retention provides continuity in the forest structure in the harvested area, and long-term surveys until the next harvest will reveal the degree of structural and compositional enrichment of the plantations.
Many landslides occurred in the torrential rain hit in the northern Kyusyu Island (Fukuoka and Oita Prefectures) from July 5th to 6th 2017. We investigated the relationship between the distribution of the landslides interpreted by aerial photographs and the radar rainfall data by the Japan Meteorological Agency. Most of landslides had occurred in the narrow area (approximately 5 km in length from the north to the south and approximately 15 km from the east to the west) where total rainfall reached to 500 mm in 12 hours.