The present study verified the practical procedures of excavator-based scarification to promote natural regeneration after clear cutting of the Abies sachalinensis plantations in Hokkaido. We analyzed the operational efficiency as well as extent of vegetation removal for excavator-based scarification using a grapple bucket and a grapple loader. This was performed in relation with the strip width of the operation and practical way of attachment. The study confirmed that the operational efficiency varied according to the operation strip width. A 5-m-wide strip showed the maximum efficiency per unit cutting area. In the grapple bucket operation, the present study compared two different practical ways of operating attachments. However, no significant differences with regard to operational efficiency between the “pull over” and “push away” treatments of bucket were observed. Moreover, the “pull over treatment” was more efficient than the “push away treatment.” The amount of bamboo root removed from surface soils were more using the “pull over treatment” in comparison with the “push away treatment.”

Consistent clearcutting and reforestation operations are increasing in Japan. It is expected that the reuse of logging machines after clearcutting processes for the purpose of site preparation would result in cost reduction and work efficiency improvement. In the present study, we compared the productivities and costs of manpower site preparation with those of mechanical site preparation using a bucket excavator and grapple loader. The study was conducted at four clearcutting sites at Nagano, Japan having gentle to medium slopes. The results demonstrated that the mechanical site preparation increased labor productivities to the tune of 2–12 times and decreased cost up to 14%–90% in comparison with manpower. It was also noticed that the volume of stacked branches and short logs affected both cost as well as productivity of the mechanical site preparation. Further, both machines greatly reduced operation costs when the stacked volume was small. Contrarily, no significant effects on cost reduction were observed when the stacked volume was large. Multiple regression equations were developed based on the relationships between the angles of worksite slopes and stacked volumes. Moreover, the relationship between the productivities of bucket excavator and grapple loader also contributed toward the regression equation. The results clearly demonstrated the feasibility of estimating the bucket excavator’s site preparation productivities prior to clearcutting, by inputting the stack volume amounts. The above method considered the wood condition before cutting and the worksite slope angles.

In Kurotaki area, Nankoku city, Kochi Prefecture, a forest owners’ association of the area consolidated the fragmented individually managed stands, improved existing narrow spur roads and made them wide enough for 10 t trucks, and introduced more efficient harvesting systems such as swing yarders and European tower yarder. Cost for the improvement and construction of narrow spur roads was lower compared to that for construction of new wide spur roads. The operational efficiency before the improvement of roads was 0.45 m³ per person-hour for the harvesting method of winching and short transportation, whereas that after the improvement was 0.98 m³ per person-hour for the harvesting method of the tower yarder. The total cost involved in the harvesting operation and the spur road improvement was reduced from 13,817 yen per m³ to 8,895 yen per m³ after the improvement, based on the application of the result of operational efficiency obtained from the field study. However, the tower yarder system would require larger tree volume for its full performance and low logging cost because smaller tree volume does not result in lower cost.

This study analyzed the effects of clear cutting and regeneration operations, including 5-year weeding operations using log-selling methods and satellite yard utilization with log-selling reports, on profitability in the fiscal years 2014‒2016 in Utsunomiya city of Tochigi Prefecture. It was found that the maximum rate of logs directly sold to sawmills in the three fiscal years was only 14.7%, but the rates of logs to meet the standards of direct selling to sawmills accounted for 30.6%‒44.1%. To sell these logs directly to sawmills, inspection and selection should be effectively conducted on landings. The average log price increased from 9000 yen/m3 to 10500 yen/m3 in the fiscal year of 2014 if these logs with lower prices in a log auction market could be directly sold to sawmills. Furthermore, profitability increased by 645000, 217000, and 137000 yen/ha with direct selling and satellite yard utilization, which lowered selling costs by 300‒500 yen/m3 in the fiscal years 2014‒2016. This implies the importance of long-term stability of log prices and selling volumes due to contracts with sawmills for promoting clear cutting and regeneration operations.

Containerized seedlings and bare root seedlings of Cryptomeria japonica were compared with regard to survival, growth, and frequency of snow damage to verify the superiority of containerized seedlings over bare root seedlings. The seedlings were planted in May, i.e., the driest month of the year. The containerized seedlings were planted using three methods, namely shallow planting using a dibble, deep planting using a dibble, and planting using a how. Eighteen days after planting, mortality of bare root seedlings accounted for >80% of the total planting, whereas that of containerized seedlings accounted for <10% of the total planting. Thus, containerized seedlings outperformed bare root seedlings in terms of survival in dry condition. Regarding relative growth during the first growing season, the diameter growth of containerized seedlings was greater than that of bare root seedlings, and the height growth of both seedling types was equivalent, except containerized seedlings that were shallowly planted using a dibble. Regarding snow damage after the first snow season, uprooting was not observed for both seedling types. The leaning angles of containerized seedlings shallowly planted using a dibble were larger than those of bare root seedlings. In contrast, the leaning angles of containerized seedlings deeply planted using a dibble were equivalent to those of bare root seedlings.