Research was conducted on a semi-legged vehicle that is capable of moving in steep and difficult terrain for a line thinning operation. The harvesting productivity was 31.8m^3 per day. If the machine was equipped with the larger the harvesting head, the harvesting time could be reduced by 17.5%. The average travelling speed of the basemachine was 481.8 m per hour and the maximum speed was 1296.0 m per hour. The machine averaged 18.5 seconds to alternate the harvesting head and the walking pad at each movement. The travelling time (or one stroke) was 40.9 seconds. If the machine can move to the speed of 1 km per hour by equipping with two maneuverable legs instead of two stabilizers, the productivity could increase by 20%.

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Research was conducted on the worker's fatigue in the industrial forest plantation of HTISP1 and HTISP3 villages in Batu Ampar, East Kalimantan. The methods of flicker and blocking test and the workers' cumulative fatigue symptoms research technique were used in this study. The result from the flicker tests showed that the flicker value had a tendency to decrease after work had been completed. The result from the blocking tests showed that the blocking phenomenon was not recognized after enrichment planting. In the workers' cumulative fatigue symptoms research, the rates of responses were compared with the differences between the industrial forest plantation workers in Indonesia and bridge-construction workers in Japan. The rate of response of the workers' physical fatigue in Indonesia was much higher than that in Japan. We believe the cause of this is due to the heat stress climate on the equater. Although there were small differences among the workers' task, weeding activity showed the highest in most responses. Comparing the living locations, the rate of response was much higher in HTISP1. We believe the people have migrated to HTISP1 much earlier than to HTISP3 (newer migration site), thus, they have accumulated more physical fatigue than the people in HTISP3.

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We investigated the working conditions and physiological loads of industrial forest plantation workers at two villages of the model located in Batu Ampar. As a result, working conditions were found to be very severe in terms of thermal conditions. According to the standards of ACGIH (American Conference of Governmental Industrial Hygienists), working conditions in the morning could be allowable if there was enough rest time (25%work-75%rest). The RMR estimated by heart rates ranged from 4 to 8 and most work was classified into heavy or very heavy by work intensity. Weeding was found to have the highest in RMR.

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This study was designed to investigate work load, and the willingness of forest workers under different employment terms. It also discusses problems relating to the procurement of young workers, and the fostering of experienced workers. The following results were obtained: Forest workers chose forestry work as a profession out of sense of attachment to forests and forestry or out of a love for nature. They were however uneasy about the current level of income, and distressed by accumulated fatigue due to chronic low-back pain or stiff shoulders. Stress and subjective fatigue sensation persisted increasingly even after work to augment already accumulated fatigue. The frequency of shuddering and startling experiences during work was found closely correlated to the times of rest, accumulation of fatigue before work and working site. It was suggested that since the workers were often unable to take rests in which they thought they could take freely at unoccupied hours, prescheduling of rest and preassigning of a duty to signal out the sign of rest were necessary for the safe execution of work.

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We investigated the growth of planted seedlings and soil conditions in two study areas (Japanese cedar and Japanese larch planting sites) during an approximate a 10-year period following disturbance caused by the passes of logging crawler tractors, and clarified the recovery process of decreased growth of planted seedlings and the poor soil properties on skid trails and skid roads. It was estimated that in the non-eroded skid trail with organic matter, the growth of planted seedlings and soil conditions will recover to the same level as that of undisturbed areas in about 10 years after tractor logging, and in the bare skid road without organic matter, recovery to the levels of the undisturbed areas may require more than 20 years.

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Using a System Dynamics method, a "Mechanization Development Model" was built to study the process and the types of mechanization in harvesting operations in Japan. This model was built based on two assumptions (1) labor shortage causes in the development of mechanization in forestry operations in Japan, and (2) the determined size of logging companies which can produce a definite volume of timber, are able to mechanize their harvesting systems. Result from the simulation study of harvesting operations in Hokkaido showed that the forestry tasks would be mechanized partly at the first stage, total mechanization would be followed at the second stage and the total mechanized operation systems would be enlarged in the scope of operations.

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The objective of this study was to evaluate the environmental damage caused by the mobile tower-yarder operations. The main disturbance made by the operations was surface soil damage from yarding the logs. We investigated the three sites after thinning operations were completed in Miyagi Prefecture, Japan. This sites consisted of Japanese cedar (Cryptomeria japonica), from 35 to 39 years old. We investigated the extent of soil disturbance in the area and the depth of the surface soil excavated by yarding the logs. Results are summarized as follows: (1) The extent of soil disturbance area was 0 to 20% of a total harvesting site. (2) The depth of excavation was almost below 10cm. (3) Factors contributing to yarding disturbances were ground features, cable location, and clearance between the load and the ground.

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In order to detect the defects in wire ropes of tower yarder in service by nondestructive testing methods, we developed a wire rope defects detector equiped with permanent magnets that magnetize a wire rope, and with hall effect elements that can measure the components of the magnetic flux density. In this study, we made a performance test of this detecter against wire ropes used in tower yarder operation. The tower yarder system is composed of KOLLER K 303and SELPA-U carriage, and its wire ropes are IWRC6×S(19) 15mm as a skyline, 6×7 9.5mm as a mainline, and IWRC6×S(19) 10mm as a haulbackline. We made a test in 150m length of each wire rope, could find broken wires not only in outer formation of wires, but in inner one. Most damaged part had 21.65% cut of section area in one pitch of the skyline.

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