霧ケ峰草原の生産力と栄養元素循環に関する研究I

Abstract

In order to clarify the annual net production and the nutrient element circulation in montane grassland, especially of Miscanthus sinensis type and Arundinella hirta type, a series of investigations were carried out during three years (1959-1962) in Kirigamine grassland (1600-1800m above sea-level), Nagano Prefecture, central Japan. The present paper, as the first report of this series, deals with the climate, soil and vegetation in Mt. Kirigamine.1. The temperature climate is fairly cool (" warmth index" by Kira is about 48°), compared with other montane grassland in Japan. Growing period of herbs in this grassland is six months from May to October, and average duration of snow cover is about four months from mid-December till mid-April.2. The soil in Kirigamine grassland was mostly originated from volcanic ashes and was very rich in humus content. Content of nitrate nitrogen was found to be very scanty both in Miscanthus-type and Arundinella-type stand. The soil in the latter stand showed lower calcium content and less- developed granular structure of soil particles than in the former one.3. The relationship between vegetation and topography (exposure or steepness of slopes) was clarified by studying the distribution of each vegetation type in Mt. Kirigamine (Figs. 1 and 2). Sasa nipponica-type communities mostly dominated ongently south-facing slopes and on hill tops, or on such places as exposed to the prevailing south wind in winter. While Miscanthus-type and tall-herb-type communities occurred mainly on north-facing slopes.Further investigations with the belt-transect method revealed a close relationship between vegetational distribution and depth of snowdrift and of frost penetration in winter period. Miscanthus-type and tall-herb-type communities were distributed predominantly in sites where soils were protected against freezing under insulating snow cover more than 1 m deep, while Sasa-type communities occurred in sites where snow cover was very thin and frost penetration was more than 10cm. The thickest A-horizon was observed in the tall-herb type stand (about 90cm) and the thinnest in the Sasa-type stand (about 50cm).4. Maximum above-ground biomass was estimated in late August in dry weight to be 190-240g/m2 for Sasa type, 210-260g/m2 for Arundinella type and 460-500g/m2for Miscanthus-tall-herb-type communities.