中部山岳地帯乗鞍岳の微環境

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The microclimatic and edaphic conditions of the environment in Mt. Norikura (3026 m above sea-level) were investigated on the east slope of the mountain. The investigation was mainly undertaken at about the 2200 m elevation in subalpine zone (1600-2500 m) and at about the 2650 m elevation in alpine zone (2500 m the top). Vegetation at the former elevation was dominantly formed by Abies Mariesii, and vegetation at the latter elevation was dominantly formed by Pinus pumila. The temperature of above- and under-ground in summer depended on the existence of plant community on the ground. In a sleeve community for Abies Mariesii at 2350 m elevation, air-temperature above the ground was natural (max. 24.5℃ and min. 8.5℃ at 5cm distance from the ground surface), and a diurnal fluctuation in the temperature also was gentle. In bare ground at the same elevation, however, the diurnal fluctuation was great (max. 31℃ and min. 8℃ at 5cm distance from the ground surface), especially at the ground surface, i. e., 38℃ maximum temperature and 8℃ minimum temperature. In bare ground in the alpine zone, the maximum temperature at the ground surface during a year (1972-1973) was 47.5℃. It was suggested that relatively high air- and soil- temperatures at a near level to the bare-ground surface were mainly caused by this high temperature at the surface. With a rapid movement of rain water in the soil of bare ground, the high temperature at the surface in the daytime make to lower the water content of the soil, and this fact will make a worse condition for plant seed germination. Although plant seeds germinated under such worse condition, the high temperature observed here will inhibit many physiological processes in plants, because the plants growing at a higher-elevation habitat require usually lower optimum-temperature for many physiological reactions than the plants growing at a lower-elevation habitat. The minimum soil-temperature through a year, except for that in the forest in the alpine zone, was about 0℃ at all of deeper levels (5-50 cm) than 5 cm depth under the ground surface. In the forest in the alpine zone, however, the minimum soil-temperature was lower than 0℃ at all levels of depth. It is suggested that soil in the alpine zone freezes to deeper level in the forest than in the grassland or the bare ground. The layer of humus soil was thicker in the subalpine zone than the alpine one and was the thickest in a sleeve community for Abies Mariesii. With the results of the other edaphic factors analyzed here, soil formation was concluded to be more active in the subalpine zone than the alpine one. The horizontal structure of soil was observed in both forests and at these edges in the subalpine and the alpine zones, but, in the grassland and the bare ground in the alpine zone surveyed at present, the soil structure was found to be the layer formed colluvially. A few dark-brown layers found among brown or light-brown layers were clarified to contain a rich humus, and this result agreed with the conclusion obtained from the analyses of the other edaphic factors. This fact may suggest that this area in the alpine zone underwent the repeated renewals of vegetation in past times.
信州大学理学部の論文
1976-08-25

中部山岳地帯乗鞍岳の微環境

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