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Within the framework of a series of secondary succession of a subtropical evergreen broad-leaved forest, the present study was undertaken to clarify stand structure and species diversity of 18-year-old post clearcut-burn regeneration on Iriomote Island, Okinawa. Within a 0.87 ha clearcut study area, four 10 m×10 m plots were installed in the centre of each section, two burned after the clearcut while two left non-burned. After 18 years of sprouting recovery, the woody stems ≥1.0 m in height were surveyed. While the basal area, stem density, richness and Shannon-Wiener index differed significantly amongst phanerophyte types, they were not significantly different between burned and non-burned plots. The sprouting regeneration showed high species diversity for both burned and non-burned plots, higher than equivalent values for mainland of Japanese evergreen broad-leaved forests, but lower than values of a tropical rain forest in southern China. The 1,531 woody stems surveyed in all four plots included a total of 72 species in 50 genera and 30 families. The most common families were Fagaceae, Rubiaceae and Euphorbiaceae. Castanopsis sieboldii, Psychotria rubra and Styrax japonicus were the most important species. C. sieboldii, the primary dominant tree, dominated the sprouting forest with a broad distribution of heights and contributed 54.9 % of the total basal area. The complexity of the layered stratification and high species diversity suggested that sprouting regeneration occurred in a progressive succession, and the stands of both burned and non-burned may evolve into a stand similar to the primary forest before clearcut.

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In order to work out the basic data for future coastal management and coastal sand.dune vegetation conservation, vegetation patterns on dry coastal sand dunes along the Shonan Coast of Kanagawa Prefecture were investigated phytosociologically and relationships to environmental factors were analyzed. In this study, coastal vegetation was classified into four classes, nine associations and six communities including two communities unknown in the higher units. Results from principal components analysis showed that vegetation habitats clearly differed in soil nutrients, other soil properties, frequency of cleaning and number of visitors. Salsoletea komarovii, Glehnietea littoralis and Viticetea rotundifoliae appear under low soil nitrogen content and anthropogenic disturbances, and Plantaginetea maioris and communities unknown in the higher units occur on soils with high content of fine gravel and high nitrogen content. Communities of Cynodon dactylon and Oenothera laciniata occurred widely on the Shonan Coast, but their habitats differ from each other. These results could be found on coastal sand dunes under strong human activity elsewhere in Japan. Based on these results, strict limitation to human activity on sand dunes is recommended for conservation of coastal vegetation. As all vegetation types of Shonan Coast were found in Hiratsuka City and Oiso Town, coastal vegetation in these two areas should be conserved carefully (strictly).

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Viola orientalis, an endangered plant specie, generally grows in ando soils that is developed in grass-land environments; therefore, grassland maintenance is a prerequisite for the survival of this plant species. The life cycle of V. orientalis is spring ephemerals. Controlled burning is necessary for the perspective of grassland maintenance, along with the burning of litter, in order to secure the light factor. The Miscanthus type grassland is an example of a habitat environment of V. orientalis in a maintained grassland. It has deep surface soil, which is covered with a variety of plants species. At the landslide sites, some parts of a 14-years-old sliding surface function as a habitat. For V. orientalis, the effective method in greening of sliding surface is to recover the Miscanthus type grassland with deep ando soils.

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[in Japanese]

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