Recently, in Japan, cross laminated timber (CLT) has been attracting attention as a structural material. Based on this, more test data are required on CLT consisting of Japanese wood species. CLT consists of several layers of lumber that are laminated by the gluing of longitudinal and transverse layers; therefore, their strength properties are
influenced by the load direction, the direction of lumber, the grade of lumber, and layups. In this study, we prepared CLT specimens (symmetrical composition, 3-layer 3-ply, 3-layer 4-ply, 5-layer 5-ply, 5-layer 7-ply, and 7-layer 7-ply layups, and the Mx60 strength grade according to the Japanese Agricultural Standard for CLT) consisting of sugi
(Cryptomeria japonica) finger jointed lumber (width 105 mm and thickness 30 mm), and conducted the bending tests under in-plane loading. The results were as follows: (1) Layers loaded parallel to the grain are mainly effective for the bending Young’s modulus and bending strength of CLT panels under in-plane loading. (2) Bending Young’s modulus and bending strength of CLT panels under in-plane loading can be estimated from those of lumber and number of layers loaded parallel to the grain. (3) Bending Young’s modulus of CLT panels under in-plane loading can be measured by dynamic testing. (4) Bending Young’s modulus and bending strength of CLT panels under in-plane loading are strongly correlated. (5) Finger joints in lumber in the longitudinal direction on the tension side between loading points play a significant role in specimen failure.
Stand- and individual-level growth responses after intensive thinning were investigated in a 114-year-old
Cryptomeria japonica plantation in Iwate Prefecture, focusing on the effects of relatively late thinning (when the stand was 90-year-old) on growth, and on factors causing variation in individual diameter growth. Before this late thinning, stem density, the relative yield index, and the crown length ratio (crown/height) were 458 trees ha-1, 0.55, and 0.45, respectively, indicating that the stand was not crowded. The thinning removed 64％ and 53％ of trees in terms of number and volume, respectively, and reduced stem density and the relative yield index to 167 trees ha-1 and 0.27. The mean annual height growth rate after the thinning was almost the same as the value before the thinning. The mean annual diameter growth rate was 0.21 cm year-1 before the thinning, and increased to 0.43 cm year-1 after the thinning. The stand-level stem volume growth rate after the thinning was 8.20 m3 ha-1 year-1, which was not greatly lower than the pre-thinning value, 8.55 m3 ha-1 year-1. The diameter growth rate at the individual level before the thinning was found to correlate significantly with the initial diameter size at the beginning of each census period. However, this correlation became unclear after the thinning, and then re-emerged at 20 years after the thinning. Analysis using a neighborhood inter-tree competition model recognized effects of one-sided competition on diameter growth after the thinning, while the effects of two-sided competition were not observed. These results suggest that, in a well-managed old C. japonica plantation, intensive thinning at a relatively late growth stage (ca. 100 years) to keep the stand at extremely low density may be a good option for producing large-sized and high quality timber in the future when a hyper-long rotation is applied (e.g., >150 years).
Establishing forest governance through stakeholders’ participation and collaboration is becoming an important issue for realizing sustainable management of urban forests that receive diverse demands. This study examined a method for assessing governance to ensure better governance in urban forests. First, the paper discussed the concept of governance of forests and then examined methods to assess the present condition of governance. Next, Nopporo National Forest was assessed using 14 indicators available to assess governance that were extracted from a questionnaire survey distributed to citizen groups that are involved in a forest regeneration activity and other forest
related management and conservation activities as a case. It was found that the governance condition was not highly
evaluated as a whole, and financial support, in particular, was lowly evaluated. Moreover, evaluations were different
between the citizen groups that had different relationships with the National Forest Office. The study indicated that
governance evaluations of stakeholders differ by their relational differences with the forest, which suggests the
necessity of conducting a more comprehensive assessment that involves diverse stakeholders.
After the Great East Japan Earthquake, an embankment was built along the coast as a planting base by the Coastal Forest Restoration Project. It is feared that a rain pool and the hardness in a part of embankment inhibits the growth of planted trees. Thus, deep tillage has been conducted on the embankment. The effect of deep tillage and its sustainability were investigated in Natori city, Miyagi Prefecture, Japan. Deep tillage was carried out by an excavator
with a skeleton bucket. Hardness and permeability were measured by a Hasegawa-type soil penetrometer and the
constant level method, respectively. This deep tillage softened the embankment and increased its permeability. After
3 to 6 months, the embankment became hard again at a depth of 0-10 cm. In contrast, the embankment remained soft
below 10 cm deep, indicating that the effects of deep tillage were sustained at that depth for 6 months.
Social wasps, which are important agents of ecosystem services (as predators) and disservices (as stinging pests),
were collected with Malaise traps in Japanese cedar (Cryptomeria japonica) plantations in three regions of Japan (Tohoku, Shikoku, and Kyushu). Each region had 12 study stands that were categorized into the following four
types based on the type of management: 1) unthinned, old-age stands (78–102 y; OA); 2) unthinned stands (41–51
y; UT); 3) stands thinned 2–4 y before the study (36–50 y) with felled logs left on forest floors (TL) and 4) stands
similar to 3, but felled logs were removed (TR). A total of 350 individuals of 13 species (nine of Vespinae and four
of Polistinae) were collected in the three regions. For Vespinae, Vespa simillima and Vespula shidai predominated in every region, making up 38-55% and 32-52% of all vespine wasps collected, respectively. Generalized linear model (GLM) analyses, in which the type of management was used as the fixed factor and regions as the blocking factor, showed that the type of management did not affect the number of species but did affect abundance of V. simillima and Vl. shidai: OA, UT and TR had larger catches over TL in the former, and OA and UT had larger catches over TL and TR in the latter. We discussed the possible reasons why these wasps did not respond positively to thinning, which was different from the results reported for other groups of insects.