In this study, we analyzed correlations among the earlywood width (EW) and latewood width (LW) chronologies of Cryptomeria japonica, annual stem biomass increment derived from tree-ring width, climatic factors, and carbon budget of a forest ecosystem [gross primary productivity (GPP), ecosystem respiration (RE) and net ecosystem productivity (NEP)] in Takayama evergreen coniferous forest, central Japan. EW was found to show a significant positive correlation with stem biomass increment, whereas LW showed no significant correlation. EW also showed significant positive correlations with temperature from spring to summer of the previous year and from winter to spring of the current year, as well as significant positive correlations with GPP and RE during these periods. Moreover, GPP and RE showed positive correlations with temperatures during the period from winter to spring. These results indicate that the temperature from spring to summer of the previous year may affect needle production, thereby contributing to the photosynthetic capacity during the growing season of the following year, and consequently leading to a variation in EW. It is also suggested that temperature from winter to spring of the current year may affect photosynthesis, which contributes to the amounts of stored photosynthates, thereby leading to a variation in EW. Moreover, our findings indicate that the increment in stem biomass changes according to EW.
This study aims to clarify the influence of the rate of high-temperature setting on the strength properties of sugi (Cryptomeria japonica) boxed-heart square lumber with pith. Past experimental data of strength properties of sugi boxed-heart square lumber with pith treated with different rates of high-temperature setting were analyzed by Bayesian statistical modeling. The data consist of bending strength and shear strength in relation to four different drying conditions, namely three different high-temperature settings for 24, 36, 48 h with dry-bulb temperature of 120 °C and wet-bulb temperature of 90 °C, combined with subsequent conventional kiln drying, as well as air-drying for 18 months. The developed model revealed that both the bending strength and shear strength decreased by high-temperature settings for more than 24 h and subsequent kiln drying. Based on the strength for air-drying, the rate of decrease in bending strength for the treatment times of 24, 36, 48 h was 7.6%, 8.3%, 21.3% on average, respectively. Meanwhile, the rate of decrease in shear strength for the treatment times of 24, 36, 48 h was 13.9%, 19.4%, 22.1% on average, respectively. These quantitative findings are useful in determining an appropriate high-temperature setting of treatment time for sugi boxed-heart square lumber with pith.
To examine the contributions of harvested wood products (HWP) used in buildings to climate change mitigation measures, this study estimated carbon stocks in HWP in buildings for each prefecture, using statistical data on existing buildings. The results show that nationwide carbon stocks in HWP in buildings have increased over the past 30 years and were estimated at 2.3 hundred million tons of carbon in 2019, nearly 90% of which were in wooden buildings. The largest HWP carbon stocks in buildings by prefecture, in descending order, were in Tokyo, Aichi, Hokkaido, Saitama, Kanagawa, and Osaka, which have large populations. A logarithmic relationship was found between population and HWP carbon stocks in buildings by prefecture, which saturates as the population increases. Nationwide carbon stocks in buildings correspond to approximately 13% of carbon stocks in Japan's forests. The carbon stocks in buildings were larger than those in forests in Chiba, Tokyo, Kanagawa, and Osaka, showing that the function of carbon stocks in buildings is comparable to that of forests in metropolitan areas.
Strength tests of madake (Phyllostachys reticulate) and mosochiku (Phyllostachys pubescens) culms, which are useful bamboos in Japan, were conducted in the green condition. Internal diameter d was estimated from external diameter D in the culm by the known regression line d＝0.81D. Section properties in the culm were calculated from D and d. Strength properties of the culm were calculated from the assumptions that the culm was homogeneous and a hollow circular cross-section material. As a result of tests, the strength properties of the culm could be expressed by several regression lines with external diameter D as explanatory variable. Of these, regression lines of stiffness data (flexural rigidity E·I, axial rigidity E·A, torsional rigidity G·J) necessary for structural analysis of space frame are as follows, regardless of bamboo species.
Log E·I＝3.49 Log D－2.49
Log G·J＝3.90 Log D－6.60