In this study, the road network planning program for the circular forest road network with high-density and various merits was made for forest management. And the forest road network planned by the program and the actual forest road network constructed by a forest owner were compared and examined using index of operational and traffic benefits. The planning method for the main spur road and the branch spur road by the Dijkstra method was examined. The main spur road orthogonal to the contour line to reach the stand was planned along geographic features such as ridges and valleys. The branch spur road along the contour line for operations was planned at regular intervals, formed the circular forest road network. The order of the main spur road planning was changed at random while revenue and expenditure was estimated. Then, the forest road network with large balances was planned. Moreover, the density of road network was adjusted by decreasing the number of attainment points of main spur roads. As a result, the overlap of the operational areas was canceled. The program could make the forest road network with increasing balances per amount of the spur road establishment.

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A cable logging method with collector rigging was investigated. The method is a variation of the Endless-Tyler method in which added blocks regulate the track of the haul-back line. The logged area was 2.25ha of a 43-year-old Hinoki stand (thinning rate: 33% by volume). The span of the cable system was 500m. A processor was used. The productivity of the logging operation was 3.2m^3/man-day (six and a half worked hours per day). The cost of logging without rigging was 9.3 thousand yen/m^3 and the cost with rigging was 17.2 thousand yen/m^3. The rigging cost could be reduced to 3.1 thousand yen/m^3 if the adjacent area of 3.75ha is included in the logging area. The cost balance was positive with income from saw logs (10.0 thousand yen/m^3), residual logs (2.2 thousand yen/m^3), and with subsidies for thinning. A simulation revealed that reducing the unhooking operation time would reduce the cost, and that the total cost could be reduced by 10 to 20% if the carriage traveling time was shortened by up to 25% by improving the winch (investment cost of 10 million yen). The residual stand damage was 7.8% (rate of damaged trees to total remaining trees), which was remarkably low compared to using other vehicle-type logging methods (ca. 20%). However, some trees were severely damaged when logged trees moved backward and forward a great deal when they ware pulled laterally.

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This study aimed to develop a thinning system using an excavator with a long-reach grapple for prehauling operations. We examined the productivity of uphill prehauling for line thinning, and compared it with the grapple loader with winch. Finally, we evaluated the labor productivity and the harvesting cost of the whole system from felling to forwarding. The productivity of uphill prehauling for line thinning was 5.3m^3/hour, and cooperation of the prehauling operation with the felling operation was enhanced. For line thinning, the labor productivity of the whole system within around 90m from roads for uphill and downhill was 15.8m^3/man-day, and the harvesting cost was 2,925yen/m^3 which was about 600yen/m^3 lower than the system of grapple loader with winch. For point thinning, the labor productivity within around 60m from roads for uphill and downhill was 10.4m^3/man-day, and the harvesting cost was 4,129yen/m^3. Consequently, this system offers high productivity and low cost for both point and line thinning, although the number of operating days and production amount in a year should be sufficient to justify the machine cost.

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