To explicate the process and secular variation of the deterioration of wooden check dams in Nagano Prefecture, an additional investigation, using Pilodyn (a wood density tester), was undertaken of wooden check dams that had been constructed five to six years before the investigation. The results of the overall investigation revealed that the relative frequencies of Pilodyn driving depths of wooden check dams, six years after their construction, yielded a logarithmic normal distribution, and the distribution curve of wooden check dams more than four years after their construction inclined in the positive direction. The ratio of the Pilodyn driving depths of 26 mm or deeper to the overall Pilodyn driving depths was denoted as the deterioration ratio. Regarding the secular variation of deterioration, correlations were observed between the average and standard deviation of the Pilodyn driving depths and the number of elapsed years, and between the deterioration ratio and the number of elapsed years. In other words, the measurements of the Pilodyn driving depths increased with the number of elapsed years—the progress of the dam’s deterioration was confirmed. In wooden check dams without water flow, the acceleration of the Pilodyn driving depth was 3.0∼4.9 mm/year in the dam wings, similar to the 3.9∼4.8 mm/year in the dam bodies. In wooden check dams with water flow, the deterioration velocities of the dam wings and dam bodies were reduced. The acceleration of the Pilodyn driving depth in the dam bodies was found to be reduced to about 2.7 mm/year.

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It is desirable to reduce the moisture content of woody biomass in order to use it for energy production. This study investigated the natural-drying process of Sugi (Cryptomeria japonica) branches as logging residues during their storage in a clear-cut field for producing fuelwood. Three natural-drying experiments were carried out; i) drying branches in summer, ii) drying in late autumn, iii) drying branches piled with a water-proof sheet cover. In the first experiment, the initial moisture content of the fresh branches was 146% on a dry-weight basis (d.b.). The final average moisture content of the branch residues had decreased to 40%d.b. after 66 days’ drying. Another drying experiment in late autumn showed that the average moisture content of the branches decreased from 120%d.b. to 51%d.b. during a 35-day drying period. Furthermore, we evaluated the effect of a water-proof sheet on the top of the branch piles. The average moisture content of branch piles with the sheet cover decreased from 115%d.b. to 35%d.b. during 35 days’ drying in late autumn. The sheet cover protected the branch piles from wetting down and was effective in decreasing the moisture content of the branches. Natural-drying of logging residues in the field would be an efficient low-cost drying method for woody biomass.

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In Kyoto City, dwarf bamboo leaves gathered from the northern mountainous area were used until recently to wrap foods and to make yakuyoke-chimaki talismans during the Gion Matsuri Festival. In order to identify factors that played a role in the formation of the social structure that supported the preparation and use of such leaves in the city, the authors investigated how leaves were gathered and processed as well as the methods of distribution used. The results indicated that traditional gathering and processing techniques (i.e., collecting leaves with smooth undersurfaces only in the Hanase-bessho and Momoi village areas and drying them in the sun) increased the quality of the product. This suggests that the formation of the social structure in which dwarf bamboo leaves were prepared and used in Kyoto City was based on local knowledge and techniques related to leaves. However, due to the mass flowering and death of dwarf bamboo seen in Kyoto City from 2004 to 2007, leaves from other regions have now replaced those from the Hanase-bessho and Momoi village areas. Moreover, in rural areas, depopulation and aging are now progressing significantly. To ensure that the leaves are prepared and used again after the regeneration of dwarf bamboo in Kyoto City, it is important to secure a workforce for the gathering and processing of leaves, and to hand down related local knowledge and techniques to future generations.

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To quantify non-reforested area (NRA) in the Kyushu region, we analyzed the occurrence rate of NRAs in each prefecture and their spatial distribution. To determine reforestation after coniferous plantation forest clear cutting, we analyzed images to determine changes in area using multi-temporal remotely sensed imagery. We studied two periods, from 1998 to 2002 (first period) and after 2002 (second period), to determine changes in NRA between the two periods. Point-based analysis showed that the NRA occurrence rate for the entire Kyushu main island in the first and second periods was 30.9 and 24.3%, respectively. Mapping the NRA spatial distribution using GIS showed that NRAs were concentrated in specific areas in both the first and second periods, rather than being distributed uniformly in the forested regions of Kyushu. The cut area of coniferous plantation forests and NRA were totaled using the Japanese secondary mesh unit, with the NRA occurrence rate calculated via mesh unit. In comparing the first and second periods, we found that most of the meshes showing extremely high NRAs (occurrence rate >50%) were not located in the same place in the two periods. Thus, the occurrence of NRAs shifted between the two periods, with NRAs distributed more widely in the second period.

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Since 1990’s, In Kyushu region, the abandonment of sites after clear-cutting plantations is increasing rapidly in Japan. Abandoned clear-cut sites may result in reduced soil and water conservation. In this study, we investigated erosions, landslides and factors limiting vegetation recovery (e.g. Damage caused by browsing by sika deer and invasion by bamboo and luxuriant vine species) in 199 abandoned clear-cut sites in the Kyushu region. Among 199 sites, 8 sites (4.2%) showed severe erosions and landslides. However, 125 sites (62.8%) showed some factors limiting vegetation recovery. Thus, the abandoned clear-cut sites are problematic, and browsing by sika deer and invasion by bamboo or vine may add limiting vegetation recovery to this problem, although a few of severe erosions and landslides currently.

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Forest recovery at abandoned plantation clearcut sites in Kyushu region depends on the amount and type of regeneration sources (buried seeds, advanced regeneration, and dispersed seeds). At the initial stage of recovery, all types of regeneration sources were important. On the other hand, the following successional process was reflected by possibility of seed dispersal. In particular, lucidophyllous species tended to recover at abandoned sites with a higher possibility of evergreen tree seed dispersal. Deer browsing was detected as the factor preventing vegetation development which was supposed to recover from these regeneration sources. Sites under moderate or serious deer browsing pressure were mostly covered by grasses and considered as the first priority sites for labor allocation. Sites without advanced regeneration, poor number of buried seeds or no adjacent broadleaved forest, tended to have low coverage of pioneer trees at the initial stage and the dominance of pioneer species predicted to continue even after 15 years. Decisions on labor allocation to these sites should be contingent on long-term tree species recoveries. Other vegetation recovery patterns which were dominated by evergreen trees or non-pioneer deciduous trees, or those mixed with pioneer trees, have low priorities for immediate labor allocation. Nonetheless, they will also require long-term monitoring to determine whether they will progress to the target lucidophyllous forest.

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We investigated the planting density of Sugi (Cryptomeia japonica) at two experimental density plots of Obi-sugi trees in the south forest district of the national forest, Miyazaki Prefecture. There were established in 1974. Both have the same systematic experimental design formulated by Nelder (1962) with 10 density blocks in the range of 376∼10,000 stems/ha and 36 repetitions. The weakness was identified in the extreme high and low density classes on the basis of the tree size, growth rate and wood quality. The high density class included the higher volume density per ha, which became constant with a volume density greater than 1,615 stems/ha. This class included trees with lower wood quality, while the low density class included those with the lower volume density per ha. From the above analysis, we concluded that the moderate planting density, which is approximately 2,000-2,800 stems per ha, is the appropriate density for low-cost forestry.

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