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The objective of this study was to describe the temporal changes in soil properties for 8 years at an experimental site. Five plots were established in 1996 on a site with granite-derived soils: three plots with pioneer trees, one with grass, and one control(with no plants). Herbs invaded the two latter plots 3 years after establishment. We measured soil chemical properties and soil microbial biomass C in the plots for 8 years, and compared the observed values in the 8th year at the experimental site with those in four forests. The total soil C content, N content, and soil microbial biomass C all increased significantly in each of the five plots over the 8 years, and the values in the 8th year showed no differences among the plots. However, the values of soil microbial biomass C in the five plots after 8 years were still smaller than those in the four comparison forests. The smaller microbial biomass C in the study plots resulted from smaller soil total C contents and water contents compared with the corresponding levels in the four forests. The ratios of biomass C to total C(bioC/totC)were higher in the study plots than in the four forests. This suggests that microbial biomass plays an important role in nutrient cycling at the experimental site.

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The historical changes of seeding work, the typical slope revegetation method, is possible to divide into five periods as follows; 1)The early period after creation(1927-1948). 2)The spreading period of modern revegetation work with manpower(1947-1958). 3)The spreading period of rapid revegetation technique using exotic grasses with machineries(1959-1985). 4)The spreading period of rapid reforestation technique by fast growing species mainly using leguminous shrub species(1986-1995). 5)The developing period of nature restoration technique using endemic arboreous species(1996-). The evaluation basis of vegetated condition after slope seeding has been described to a official guide book, "The Standards of Slope Stabilizing Works." It was mainly revised three times after first edition in 1972, and also the point of evaluation basis changed from the vegetation coverage to the density of woody plant through the 3rd period and the 4th period. Consequently, a lot of survey reports after 1990 tend to mention only vegetation coverage, density, and height growth requested in the evaluation basis by the standards, and, the plant sociologic surveys are not used. Recently main purpose of slope seeding has been developing from the erosion protection to the nature restoration in the current of the 5th period. At present the importance of advanced monitoring methods for vegetation maintenance and plant sociologic survey to evaluate the plant succession is increasing.

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To create a population of Gagea lutea Ker-Gawl. by sowing or planting container grown individuals, the effects of storage methods, sowing time, burial depth, and light on seeds were investigated. The stage of germination was distinguished between radicle emergence from the seed coat and cotyledon emergence above ground. Seeds stored in dry conditions at 5°C for two years had radicle emergence of 90% or more; however, seeds stored in dry conditions at 25°C or room temperature had a reduced rate of radicle emergence of 30% or less. Seeds, stored in dry conditions at 5°C and sown by the beginning of September, had cotyledon emergence of 70% or more the next April. However, seeds sown after October had a reduced cotyledon emergence of 30% or less next spring. Cotyledons of some seeds sown after October did not emerge the first spring, but did so the second spring. Seeds buried at a depth of 0.5-1 cm in soil showed the cotyledon emergence of 74% or more, whereas seeds buried at a depth of 2 cm or more had reduced cotyledon emergence of 63% or less. Light conditions hardly influenced radicle emergence. The results show that G. lutea seeds do not have to be sown immediately after collection, and that high percentages of cotyledon emergence the next spring result when seeds are stored in dry conditions at 5°C, and sown before September at depths of 0.5-1 cm.

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Annual changes of the community structure of ground insects were investigated using pitfall traps at the isolated small stands in the suburbs of Tokyo and the results were analyzed by detrended correspondence analysis. Grassland species decreased as increasing of stands age and forest species appeared from 10 years after establishment of the stands. However, the community structure was thought to become simple because forest insects could not easily immigrate due to non-forest areas between isolated stands. According to the similar investigations at green lands such as grassland and hedge, the community structure was also thought to become simple at the sites of poor undergrowth and litter due to management. Therefore, not managed isolated stands were thought to be important for ground insects as habitats in the suburbs. Moreover, to make ground insect species diverse, continuous maintenance of green lands such as forest and grassland was considered to be important.

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In the revegetation technique that uses forest topsoil, topsoil is spread over bare land, leading to the germination of buried seeds, thereby creating a pioneer plant community. This revegetation method is known as useful one for preventing erosion and conserving the biodiversity of artificial banked slopes in Japan. This study examined a spraying method using forest topsoil on an artificial cut slope in Tochigi Prefecture, Japan. Topsoil containing 35.4 buried viable seeds/L was collected from a forest by hand to a depth of approximately 5 cm and used to revegetate a cut slope oriented in a SW direction and inclined 66°. The soil was mixed with growth base material in 10, 20, or 30% proportions and used in different areas. After three years, many species emerged at each site, and the coverage ratio was approximately 50% at all of the study sites. This suggests that revegetation will occur when forest soil is mixed in a ratio as low as 10%. Coverage is increased by using topsoil ratios of 20 or 30%. Nevertheless, the results were inferior to past studies of artificial banked slopes. Moreover, in the study, there was few species dispersed from the surrounding vegetation and grew in the slope. The method must be improved in these respects. We also compared the understory vegetation at the site where the topsoil was collected three years after collecting, with that before the topsoil was collected. The emerging species, emergence frequency, and degree of cover of each species were measured. The number of emerging species and total degree of cover increased after collection. This suggests that collecting topsoil to a depth of approximately 5 cm manually does not affect the forest understory vegetation.

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The Hokkaido-Nansei-Oki earthquake that occurred on July 12, 1993, caused major damage to the slope about 150 km from the epicenter. Nihon University Experimental Forest at Yakumo is located about 100 km apart from the epicenter. The area is covered with hard shale and the pelitic sandstone of the Yakumo Formation. There are about 35 large landslides in this areas. There are only a few reports on the aerial photographic analysis of the process of the recovery of vegetation on landslides. In this study, the process from the occurrence of a landslide to vegetation recovery was discussed with respect to expansion, combination, shrinkage and separation. The landslide land was analyzed based on the aerial photographs taken in 1967, 1983 and 1998. The results are summarized as follows: 1)There was no major change in the distribution of landslides in the past 31 years. 2)Landslide has occurred at 583 sites in 1967, 540 sites in 1983 and 541 sites in 1998. The decrease in the number of landslides after 1967 may have been the result of afforestation. Only a few nets had been produced by the Hokkaido-Nansei-Oki earthquake in 1993. 3)There was confirmed to be a landslide area of 86.9 ha in 1967, 86.1 ha in 1983, and 103.4 ha in 1998, and was largest in 1998. This may have been because even a slight earthquake movement weakened the volcanic ash layer of the soil surface, and subsequent rainfall promoted the expansion of landslides. 4)Most of the landslide sites in the study area were about 0.2 ha. 5)The average expansion coefficient for the sites was 1.53-1.56, and the damaged sites were circular or elliptical in shape. 6)Damaged sites were mostly steep with a slope angle of 30-45°. 7)Many of the slopes with damaged sites faced north, northeast or east. 8)In the study area, the expansion-type of landslide was dominant.

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[in Japanese]

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[in Japanese]

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