In Japan, it has been reported that soil erosion often occurs in hinoki (Chamaecyparis obtusa) stand. This study clarified the effects of sugi (Cryptomeria japonica) and hinoki leaves on the prevention of surface flow and soil erosion. Some factors which affects eroded soil amount were analyzed by using ANOVA. As a result, the factors and interactions of rainfall intensity, rainfall intensity × land-cover amount and land-cover amount had the higher contributing portions. Land-cover type had a little effect on eroded soil amount and hinoki leaves were found no less effective for soil conservation than sugi leaves. In addition, some factors which would affect surface flow were also analyzed by using ANOVA. As a result, the factors of rainfall intensity and land-cover amount had the higher contributing portions. It was found that land-cover of leaves prevented surface flow which causes soil erosion. In this study, tank models were also employed to explain the mechanism of surface flow. The results showed that splash impacts broke aggregated structure and infiltration rate decreased with less land-cover, and that water storage on surface increased with increased land-cover because of raindrops attached to leaves on the ground. It was also confirmed by using tank models that hinoki leaves were almost as effective as sugi leaves for soil conservation. In conclusion, it is beneficial that leaves taken out of forest lands by logging is returned to the original forest lands in terms of land conservation.

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In this study, we estimated the work of machine operators who use a screen display to obtain visual information, and examined the effects of the combination of working hours and working posture on the result and load of the work. The results are as follows : 1) During the continuously operating work in a cabin, mental load in a seated posture tended to be heavier than that in a standing posture. 2) The increase in heart rate was alleviated by starting the work in a seated posture followed by that in a standing posture. The workers operating continuously for a long period complained of severe stress, and the change of work type reduced the stress. 3) The longer the continuously operating work, the worse became the work results, and the results were improved by repeatedly changing the work type within a short time. In particular, "overlooking" occurred frequently during the continuous long-hour work in a seated posture, and the frequency was extremely lowered by changing the work types within a short time. "Overlooking" is one of the work mistakes made during the operating work, and its frequency is considered to correlate with labor hazards. Thus, in these operations, long monotonous work is considered to be hazard of labor accidents.

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In the recent years, we are not able to manage forest regions without considering natural environment and protection of natural forest resources. Therefore, it is necessary to develop the system to evaluate constitution factors of the forestscape as forest spatial potential resources in detail. In order to understand the forestscape, we classified constitution factors of that by the imagery data processing method and the aerial photograph of Mie University Forest. In this study, we used color orthophotos for measuring the right positions and areas. With the personal computer and the scanning sencer, the orthophoto was processed into digital image data. As a result of this investigation, it was ascertained that each constitution factor of the forestscape in the digitized aerial photograph had the characteristic tone of RGB. We classified constitution factors of the forestscape by tone of RGB. This method was effective. Moreover, by integrating these factors, we could accurately grasp the forestscape in larger area.

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The objectives of this study are to apply differential GPS to several kinds of work for forest management and to clarify the accuracy of GPS surveying in mountainous areas. The surveying method used was code differential system. At first, we drove a car on forest roads with a GPS receiver several times. After that, these forest roads were illustrated accurately enough by connecting tracks. Next, we walked along forest boundaries with a GPS receiver. These boundaries were also illustrated accurately enough by removing wrong points taking walk speed into account. The results showed that it was possible to locate forest roads or forest boundaries on topographic maps of 1/5,000 scale by GPS surveying. The accuracy of GPS surveying was reduced in forests, but it was not on condition that more than five GPS satellites were logged or PDOP was less than 5. In addition, the average error of GPS surveying of control points, which was done on one point 30 times for 30 seconds, was found to be 2.86m (7.42mCEP_<95>) in horizontal direction and 4.71m (12.04mCEP_<95>) in horizontal and vertical direction. However, it was reduced to 1.32m in horizontal direction by repeating measurements four times on one point. In conclusion, GPS surveying of forest roads and forest boundaries is feasible in mountainous areas where it is often difficult to capture GPS satellites.

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The objective of this research is to develop a computer program to simulate the harvesting design by means of a cable yarding system for a personal computer. The cable yarding design for a mobile tower yarder intended for thinning on steep terrain was explored through the use of geometric analysis and a simple algebraic expression for cost of logging. For a given different kinds of harvesting situations, our approach could provide a very useful way of determining how many cable lines and yard points for setting are needed from the point of view of the minimized the total sum of production cost, where the costs are assumed to be significantly affected by the number of cable lines and yard points. The methodology calculates the costs which were composed of the setting cost for cable lines and yard points, system moves cost among yard points, prehauling and yarding cost, to maximize the defined profit objective. The procedures greatly reduce the computational complexity of the problem and makes it possible to solve for the most efficient design given alternative modes of timber yarding with a mobile tower yarder. Performance evaluations were made under a variety of operating conditions, especially uphill and downhill, types of tower yarder and harvesting restrictions (non-uniform yarding distance, irregular boundary shapes, unequal distance between multiple yard points), and then selected the most suitable number of cable lines and yarding point. This paper presents the general formulation of the problem, describe the solution, offer an illustrative example and explore some extensions of the method.

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