Recently, it has become important to reconsider low-cost silviculture for replantation. In this study, we evaluated the relationship between replanted tree height growth and state of competition with weeds in replanted Sugi (Cryptomeria japonica) forests. The results showed that the amount of weeds affected the height growth and workload of weeding. We should also encourage the reporting and comparison of further experiments of weeding and growth surveys.

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Line thinning was conducted in a conifer plantation to facilitate the establishment of broadleaf seedlings and transition to a mixed forest. We investigated the effects of slope direction on the community structure of understory trees (height ≥ 20 cm), as well as light and soil environments, in thinned and unthinned lines in a 40-year-old Japanese cypress plantation 4 years after line thinning. In 4-m^2 quadrats, the heights of understory trees were greater on the south-facing slope than on the north-facing slope, and the heights, number, species, and evenness (J') of understory trees were greater in thinned lines than in unthinned lines. However, tree height was the only difference found in the total of 24 m^2 of quadrats (six quadrats, in replication). In the 4-m^2 quadrats on the south-facing slope, the light environment and soil pH were higher, whereas water content, C/N ratio, and available soil P were lower than on the north-facing slope. Water content was also higher in the thinned lines. Principal component analysis and generalized linear models suggested that the number of understory trees decreases with brightness and dryness and increases with nitrogen availability. In addition, evenness decreases and tree height increases with nitrogen availability. As the community structure of understory trees is affected by environmental differences between north- and south-facing slopes on a long-term basis, topographical environmental differences should be taken into account when conducting line thinning.

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In 2005, the primary infection of zonate leaf blight disease of Calera japonica and the effect of removal of the primary inoculum on disease occurrence were tested in a plantation in Tsuwano Town, Shimane. The number of propagules produced on the branches (dead branches) that had grown, and afterwards, had died of the disease in the previous year was investigated. The propagules were produced from mid April to early July. In particular, a number of propagules were produced after a few rainy days in early July. However, no propagule was produced on and after mid July. In late May, dead branches-removing treatment was conducted. As a result, the incidence of diseased leaves was low in the treated trees. However, the incidence of diseased leaves in untreated trees was observed in and after mid July and was prominent in early August. Thus, it was suggested that the primary inoculum consists of the propagules produced on the branches that had grown, and afterwards, had died of the disease in the previous year. It was also shown that the removal of the dead branches before the primary infection prevented the primary infection of the disease.

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This study clarifies the change in the local wood production and supply structure and the response of the existing competing business entity (Yamasaki Wood Market Co., Ltd.) to the start-up of the new large-scale sawmill (Cooperative Hyogo Wood Center), the material woods of which are mainly supplied by loggers, in Shiso city, Hyogo prefecture. The National Forest and Shiso Municipal Forest have changed their wood supply methods, whereby the National Forest has opted to sell only to the Cooperative Hyogo Wood Center. Conversely, the Shiso Municipal Forest has adopted equity in supplying wood to two companies. In contrast, most other forestry corporations and one forest owner cooperative have retained unchanged methods of wood supply and prioritize the longheld business custom with Yamasaki wood market, collaborating as a group. Yamasaki wood market began to promote tree-cutting to forest owners to increase and stabilize the volume of wood supplied. Consequently, based on two competing companies co-existing in proximity, the volume of wood supplied in that area has increased. This approach to wood supply, as adopted by the local forestry companies, looks set to remain unchanged for a while.

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