Soil movement and physical properties of surface soils were measured at 263 points in the evergreen broad-leaved Aya forest in southern Kyushu, in order to clarify the factors affecting the establishment and survival of seedlings. The mass of soil movement was found to be different in each microtopographical unit. Depositional poits were observed on crest slopes where the angle of slope was gentle, whereas the headmost wall and head hollow, where the angle of slope was steep, demonstrated heavy soil denudation. This denudation is thought to be caused by surface runoff during the heavy rains. Temporal changes in soil movement, the variations in accumulation and denudation, were large in the head hollow and the footslope and depended on the amount of precipitation. In the crest slope, the upper sideslope and the headmost wall, erosion was found to occur from spring to autumn, while deposition occurred from autumn to spring. Porosity in the low suction range, which increases permeability, showed high values on the crest slopes and the upper sideslopes. Porosity in the high suction range, which increases water retention, showed high values on the upper sideslopes and the head hollow. The soil water content in situ was found to be in proportion to the level of high suction range porosity. On the other hand, the soil water content in situ was in inverse proportion to the level of low suction range porosity. From the relationship between physical properties of surface soils and erosion rates, it is clear that the soils which have high level of low suction range porosity show less erosion rate.

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Habitat of Pinus koraiensis and its cohabiting tree species was surveyed on the rocky fields in the mature subalpine coniferous forest around Shirakoma pond, northern part of Yatsugatake mountains, central Honshu, Japan. Tsuga diversifolia prevailed throughout in the forest with the relative basal area of 45%, followed by Abies and Betula spp., and Picea jezoensis var. hondoensis. Pinus koraiensis occurred only sporadically, being subordinate species with the relative basal area of 8%. On the sites with poor rocks, Abies and Betula spp., and P. jezoensis var. hondoensis co-occurred abundantly with T. diversifolia. P. koraiensis scarcely occurred there. On the sites with abundant rocks, P. koraiensis constantly appeared, being second dominant of T. diversifolia. Abies and Betula spp. sharply reduced their occurrences there. Consequently P. koraiensis may have more opportunity to establish there.

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In order to clarify the relationship between revegetation and site environments during the first 10years on the 1984 Ontake debris avalanche deposits, two transect lines were set up at Tanohara (2000m.a.s.l.) and Korigase (950m.a.s.l.). Topographical survey, grain-size analysis and vegetation investigation were carried out along the lines. At Tanohara, where the wavelike relief was formed by the debris avalanche deposits, there was no significant difference in the number of species and coverage between the plots which have more than 5% of fine earth content in spite of topographical variations. However, in the troughs which have been susceptible to the influence of running water, dispersion of fine earth content varied widely and the number of species and coverage in a plot which has only 1% of fine earth content was extremely low. At Korigase, the debris avalanche deposits which had buried the river bed of the Otaki River were dissected and a three-tiered terrace was formed. The number of species, maximum height of vegetation and coverage were highest on the top terrace, which is an original depositional surface of the debris avalanche and has been free from river erosion. This result suggests that the erosional process by running water is one of the important factors affecting vegetation development on debris avalanche deposits. Compared with Tanohara situated at a higher elevation, maximum height of vegetation and sum of cover percentage of each species on the top terrace were significantly higher.

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