A soil layer with a penetration resistance of less than 1.0 was detected at the depth of the slip surface on a weathered granite slope and was named the "fragile layer". This layer was assumed to be a key to understanding the surface failure process and its characteristics were examined by various soil tests. The internal friction angle of the saturated soil from the fragile layer was as low as 1114 degrees. This low angle was attributed to the destruction of the soil structure, called "collapse, " by saturation occurring before the shearing test. The fragile layer soil in the water absorbing process abruptly subsided when it became saturated. The fragile layer characteristically has a much higher void ratio than the upper or lower layer, the volumetric ratio of coarse sand particles is as high as 0.85 to 2.0 mm and the ratio of pores 2.0 to 4.75 mm in diameter is also high. The coarse sand particles that construct the skeleton of the fragile layer, therefore, easily tumble into the pores. By microscopic observation, such tumbling was confirmed to occur in the soil at saturation. This phenomenon could result in reduction of the total volume, i.e., collapse settlement. Collapse settlement occurring in the fragile layer hidden in the slope might play a significant role in the surface failure phenomenon.

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Abies koreana is an endemic and endangered species in Korea. To understandthe seed germination characteristics of A. koreana, germination response was examined under different cold stratification periods, temperature conditions, and drought regimes with comparison to Abies sachalinensis, seedlings of which occur densely in natural forests in Hokkaido, Japan. Cold stratification of 30150 days increased the germination speed and final germination rate in both species. In seeds with the cold stratification of 150 days, final germination rates at 1030°C were 1.78.5 (42.987.8%) and 2.19.2 (72.189.8%) times those of unstratified seeds in A. koreana and A. sachalinensis, respectively. However, A. koreana seeds germinated more slowly than A. sachalinensis seeds, and took about 40 days to reach the final germination rates at 1030°C. Increase in germination rates of A. koreana depended on cold stratification periods and temperature conditions of the germination test. Cold stratification especially increased the germination rate under cold temperature conditions. Longer cold stratification was necessary for A. koreana compared with A. sachalinensis. Cold stratified seeds of the two species were not affected in germination rates by a non-watered condition of 6 days. However, the germination rates of cold stratified seeds of A. koreana decreased significantly with decreased water potential adjusted by polyethylene glycol 6, 000 solutions, and declined to approximately 50% of control seeds at -0.4 MPa of water potential. In contrast, cold stratified seeds of A. sachalinensis were germinated to approximately 80% of control seeds at -0.8 MPa of water potential. Consequently, it is assumed that the germination period of A. koreana seeds is longer than that of A. sachalinensis so it is easy for A. koreana seeds to avoid damage such as late frost injury, although its drought tolerance is weaker than that of A. sachalinensis.

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The effects of forest cutting on nutrient dynamics, soil water content and chemistry, and stream water discharge rates and chemistry were examined for three years after the partial (lower slope ; 20% of total area) forest cutting of a watershed composed of artificial stands of old (99 years) Japanese cedar and cypress in Gunma prefecture, Japan. After the forest cutting, the soil water content in the surface soil layer (010 cm) decreased, although it increased in a deeper layer (3060 cm). The annual stream water discharge increased by about 100 mm after forest cutting. Compared to the period before cutting, the concentrations of NO₃^-, Ca²⁺, Mg²⁺, and K⁺ in surface soil water (5 cm) also increased during the summers of the first two years by about 37 times. However, three years after forest cutting, the concentrations decreased to the same levels as those in the period before cutting. Similarly, the stream water concentrations of NO₃^-, Ca²⁺, and Mg²⁺ increased 1.5 times. Seasonal changes in the concentrations of all analyzed ions in stream water increased in comparison with those before cutting. After forest cutting, the amount of NO₃^--N in the 3060 cm layer increased by four times the amount before cutting. Furthermore, this large amount persisted during the three consecutive years after the forest cutting. The NO₃^--N export to stream water increased up to 4.05.0 kg ha^-1 yr^-1 after cutting. However, the increase in the amount of NO₃^--N leaching to stream was smaller than that in soil water; this indicates the great potential of soil as a medium for NO₃^--N export. A higher amount of NO₃^--N in deeper soil (>30 cm) suggests retention and/or consumption of this ion in the soil even after the forest cutting.

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TheChinese national forest system, which has developed logging from natural forest, faces two problems, sustainable forest use and community management. Multiple management is the key to meet these problems. With this paper, the historical development of multiple management of Chinese national forest is clarified from the viewpoint of whether management is based on group or family, and resources are oriented from the forest or not. Group-based multiple management has contributed to the core enterprise by functioning as unemployment compensation. Although family management, which was a part of the individual enterprise of workers, had contributed to community development, it was severely damaged during the Cultural Revolution. Development with group management had been directed officially through the 1970's and 80's, but family management did not been flower until the economic reform of the 1990's. Since the later half of the 1990's Chinese forest policy has made much of multiple management under the crucial conditions of forest resources. Now it is at a stage in which group-based and family-based management are both groping for a way foward further development. While Chinese national forest service intends the development of non-forestry and multiple management, the management which it depends on must wait for social recoanition of thevalue of sustainable community management of national forest.

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To understand environmental effects on cedar growth, the ratio of deciduous broadleaves in cedar plantations was analyzed using a simple and generalized method. A forest type map of four forest classes (Evergreen, Mixed-A, Mixed-B, and Deciduous) was created using forest management information in a geographical information system. Topographic effects in two TM images taken in June 1994 and September 1996 were removed using the pattern decomposition method. The surface area in the images was classified by the ISODATA method into 25 categories, which were grouped into 7 classes including the 4 forest classes by reference to the forest type map. A classification map was created by assigning each pixel to either the evergreen or deciduous class. Finally, sub-compartments were classified as evergreen, mixed or deciduous classes based on the ratio of deciduous pixels in the sub-compartments. The accuracy index, KHAT, was 0.773. The classification map showed that the ratio of deciduous pixels was higher in forests on steeper slopes, and increased at elevations over 800 m. These results suggest that snow gliding, deep snow and cold air temperature inhibited cedar growth. The resultant map showed the mixing ratio of deciduous trees in cedar plantations, which should be useful for forest management, such as finding suitable areas for cedar plantations.

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We investigated the relationship between individual tree heights and topographic factors of their standing positions, such as the distance from a ridge (d_r), the distance from a flow path (d_f), the position on a slope (d_r/ (d_r+ d_f)), the slope angle, the slope aspect and the altitude, in a Chamaecyparis obtusa stand located in the Kagehira-Ichinomatayama National Forest in Kochi Prefecture. We compared individual tree heights derived from the field survey with those obtained from airborne laser scanner data for a 0.5 ha sample plot to confirm the accuracy of the identification by airborne laser scanner. The correlation coefficient between tree heights derived from airborne laser scanner data and those derived from the field survey was 0.94. All tree heights and topographic factors in the study area were calculated from the airborne laser scanner data. We performed a multiple regression analysis, using tree height and topographic factors as the dependent variable and the independent variables, respectively. As a result, the multiple correlation coefficient was 0.71 and the analysis made it clear that the tree height of Chamaecyparis obtusa depended on the position on a slope and the altitude.

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We proposed a statistical method to search for factors affecting the target forest stand growth. The method consists of multivariate linear modeling and selection of an optimal model for such factors based on the information criterion in the following way. First, by fitting a growth curve model to the growth data for each tree, coefficients of the growth curve model are estimated. Then, by setting the estimated coefficients as new response variables, several multivariate linear models are constructed with different sets of explanatory variables possibly affecting the growth. Among a set of the derived multivariate linear models, an optimal model is sought by minimizing the cross-validation criterion for the final set of factors. We applied the proposed method to both the diameter and height growth data from a sugi (Cryptomeria japonica) sample plot set in one of Hoshino village forests in the Yame region, Fukuoka Prefecture. Our example showed that the current DBH (diameter at breast height) of the target tree and, , the distance-weighted average DBH of the surrounding trees are found to be the final explanatory variables.

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Land-use zoning, which was developed as an urban planning method, has been used in the planning of natural areas. In addition to the designation of protected and recreational forests, a recent functional zoning under comprehensive forest planning allocates a specific zone to recreational uses. In nature parks, a complicated zoning system has been developed. However, its application is limited to resource protection, especially scenic resoures. Recreational activities had been excluded from the system until the introduction of visitation control zones in 2003. From such historical analyses, it became clear that recreational zonings have not fully expanded in Japan. On the other hand, an analysis of the Recreation Opportunity Spectrum (ROS) concept revealed that recreational application of zoning is possible in the case of factors of opportunity settings like facilities. Combined with density control as applied in Adirondack Park and with corridor protection in the national trails system, both in the United States, recreational opportunity zoning will be a powerful tool to cope with overuse issues through the regulation of facilities such as trails or huts.

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