When forestry workers prune away and lop branches off a tree using a chainsaw, they do so from various directions considering the possible deflection of the branches to prevent branch-bite. When using a robot with a chainsaw attached, it may get stuck halfway due to branch-bite caused by cutting in one direction. This paper formulates the contact force where a branch is cut at the contact point between the guide bar and the branch, and estimates the required driving force for the robot to cut and proceed. Experiments were conducted using a branch cutting machine that reproduces branch-bite to compare the currents flowing in the driving motor for the cases with and without an anti-branch-bite mechanism. The currents measured for the case with and without the anti-branch-bite mechanism were 85.5±17.2 and 148.9±20.7 mA, respectively. A significant test (Man-Whitney U-test, p<0.05) was conducted and it shows that the proposed mechanism outperforms the conventional one. The proposed branch-bite prevention mechanism was shown to prevent branch-bite effectively and reduce the reaction force received when cutting and proceeding by spreading the incision of the branch using circular orbit cutting.
We investigated how height growth and suppression by weed of planted sugi trees (Cryptomeria japonica) differed with topographic variables along a slope (distance from the ridge and slope angle). We also assessed different statistical models to detect these relationships. We developed three types of models (without random effects, with random effects and with spatial autocorrelation) to predict three and four years old sugi tree height, conditions of suppression by weed and topographic variables measured at 16 subplots along a slope. Sugi trees further from the ridge were taller. The probability of being suppressed by weed was higher for sugi trees that were shorter, or further from the ridge, or on a steeper slope. These effects of topographic variables were reduced in the spatial auto-correlation model, with corresponding increases in credible intervals. We concluded that the reduction in weeding frequency within a stand along a slope may be one possible option in low-cost weeding management, but sampling and statistical approaches methods must take care to evaluate topographic effects with spatial information.
The objective of this study was to develop a methodology to detect potential introduction and harvesting areas for an H-type logging cable system by means of a geographic information system. Using the digital elevation model, the logging cable level was first computed by calculating the mean value in a neighborhood circle with a 750-m radius, which is the actual span of the H-type logging cable system introduced in Odai, Japan. By subtracting the elevation from the logging cable level, a potential introduction area was detected while considering midspan deflection. After inputting information of the road network and plantation distribution, a harvesting potential map was developed. The total potential harvesting area was calculated as 1,045 ha of the total plantation area (14,911 ha). The computed potential harvesting area covered most of the area and was 1.26 ha larger than the actual harvested area. The larger estimation was due to the actual level of the logging cable being lower than that calculated by our study. Thus, the larger value obtained was in line with expectations. Although several issues, including the tendency to overestimate the lifting wire deflection, require further investigation, the proposed methodology easily detects potential introduction and harvesting areas for an H-type logging cable system for a wide area. Therefore, these results will assist in the determination of an appropriate harvesting system.
Kureha Hill (KR) and Imizu Hill (IM) are located adjacent to one another in the center of the Toyama Plain. Though the recent nitrogen (N) loadings on them are almost same, N output from KR exceeded about 17 times that from IM. Therefore, a previous study indicated that the forest ecosystem at the KR site was N-saturated. To elucidate the mechanism underlying N-saturation in KR using a kinetic N-saturation model, we examined the N sink components of the ecosystem, i.e., N retention in plants and soil and N leaching into hillside streams. The soil N pools did not differ significantly between the two sites, but the net N mineralization and nitrification rates of surface soils (depth: 0–10 cm) were significantly higher in the KR. Foliar N concentrations and litter N cycling rates from plants to soil were higher on the KR hillside, indicating that plant N retention in this site exceeded retention levels in IM. Stream nitrate concentrations were higher in water samples collected in KR, indicating that outward N leaching rates were higher in this site than in IM. High N retention levels in plants in the KR likely increase the rate of litter N cycling, which may in turn accelerate rates of surface soil N mineralization, nitrification, and N leaching. These mechanisms may explain the kinetic N-saturation levels at the KR.
We analyzed the historical changes in the nature, supply, and provision of biomass resources in terms of fuel sources supply on Tarama Island, Okinawa, Japan, to clarify the situation regarding the local community and governmental regulation. A sugar industry was developed on the island in 1898, which resulted in higher demand for both fuel for use in sugar production and lumber for processing into sugar barrels. Bagasse and forest litter were used as fuel sources for sugar production. Meanwhile, the lumber for processing into barrels was imported. These conditions allowed for adequate supply of household fuel sources to continue. However, the consumption of forest litter for fuel was increasing competed with its alternate use as a fertilizer for farmland, leading to diminished productivity of the island farmland. An afforestation plan was made in 1917 by using Pinus luchuensis in order to create a communal forest. However, because felling in a communal forest was prohibited, the value of private forest increased. Subsequently, in 1938, the government encouraged afforestation P. luchuensis and Casuarina equisetifolia. Consequently, private forest area increased, and it became possible to supply barrel lumber. In the periods of postwar, the population decline and barrel became paper box allowed the exported of fuelwood. The afforestation declined by the spread of alternative fuels after the 1960s. These governmental regulations concerning biomass resources effectively led to self-sufficient fuel sources production.
To insure a stable demand of Japanese lacquer, evaluation of suitable plantation sites for lacquer trees, Toxicodendron vernicifluum (Stokes) F.A. Barkley, is urgently needed. In this study, the relationship between lacquer tree growth and environmental factors and/or and stand conditions was examined at 111 plantation sites in Aomori, Iwate, Niigata, and Ibaraki Prefectures. Statistical analysis was carried out using a generalized linear mixed model (GLMM) in which the mean tree diameter at breast height (DBH) was the response variable, and six fixed effects (stand density, slope orientation, soil type, annual mean temperature, maximum snow depth, and ivy damage) and a random effect (prefecture) served as the explanatory variables. The most appropriate model was selected based on Akaike's Information Criterion. We found that the positive coefficient of annual mean temperature and the negative coefficient of maximum snow depth accounted for most of the variation in DBH in the selected model. This is the first study to evaluate environmental effects on lacquer tree growth based on such a detailed measurement of environmental parameters. This study provides sufficient information for evaluating suitable sites for lacquer tree plantations.
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Edited and published by : The Japanese Forest Society Produced and listed by : Center for Academic Publications Japan/Shobi printing Co., Ltd. (Vol.96 No.2-) Center for Academic Publications Japan/Fukasawa Ltd. (Vol.91 No.3-Vol.96 No.1) Center for Academic Publications Japan/Daishowa Printing Co., Ltd(Vol.88 No.1-Vol.91 No.2)