Historical changes of semi-natural grasslands in the central mountainous area of Japan and their implications for conservation of grassland species

Tremendous reduction of semi-natural grasslands during the 20th century in Japan caused crucial threat to grassland species such as plants and insects. It has also raised concerns about historical changes of anthropogenic disturbance on vegetation and traditional land use. However, the postglacial history of human interference on semi-natural grasslands in the Japanese islands is scarcely known. In the present paper a primary sketch for the throughout history of the semi-natural grasslands is proposed with special reference to the central mountainous area of Japan. Various species since glacial periods have remained in relatively well assembled semi-natural grasslands such as volcanic slope meadows in this area. Existence of andosol, called 'kuroboku', widely distributed in Japan indicates the locations of the past semi-natural grasslands along with the fact that it contains microscopic charcoal. Recent studies of the microscopic charcoal show fire disturbances probably caused by humans had abruptly increased since the Jomon era (the early Holocene). Pasturage of horses had become prominent in the central mountainous area since the ancient age. Capitalization and population growth of the Japanese society in the early modern period (including the Edo era) greatly intensified usages of grasses and shrubs from meadows. However, industrialization since the 19th century has immensely diminished the usage of the semi-natural grasslands. Alongside all this history, grassland species could find persistent refuges where large or many of adjacent semi-natural grasslands have been maintained for long periods by humans. To identify the locations of these continual habitats for conservation and restoration of the grassland species, distribution data of (1) vegetation and land use, (2) andosol and the microscopic charcoal, (3) the species, phylogenic lineages and genetic variations, (4) human interferences indicated in historical documents are available.