Species Composition and Environmental Factors of Abies homolepis Forest around Mt. Yatsugatake

Species composition and environmental factors of the Abies homolepis forest are investigated around Mt. Yatsugatake in Central Japan. Based on the phytosociological classification, Abies homolepis forests in this area are classified into two communities: Rhododendron wadanum-Abies homolepis and Lonicera demissa-Abies homolepis communities. The former is differentiated by Rhododendron wadanum, Acer distylum, Arachniodes mutica, Fagus crenata and Fagus japonica; the latter, by Lonicera demissa, Schisandra chinensis and Ligustrum tschonoski. The Rhododendron wadanum-Abies homolepis community is divided into three lower units: Sasa nipponica, Cacalia yatabei, and Carex reinii. Lonicera demissa-Abies homolepis community is divided into two lower units, Meehania urticifolia and Waldsteinia ternata. The relationship of these community types to climate as an environmental factor is investigated. The Rhododendron wadanum-Abies homolepis community (except for Carex reinii lower unit) occurs where Kira's coldness index is higher than -33℃・month. However, The Lonicera demissa-Abies homolepis community occurs where the coldness index is lower than -37℃・month (Fig. 6). Based on the geological map of this area (Fig. 4), the Lonicera demissa-Abies homolepis community occurs in the volcanic area of Mt. Yatsugatake and Kirigamine. Moreover, Meehania urticifolia lower unit occurs on upper valleys and Waldsteinia ternata lower unit occurs on terraces in valleys. In this syudy, the terraces in this region are covered by rocks of lava which were deposited in valleys by volcanoes. On the other hand, Rhododendron wadanum-Abies homolepis community does not occur in volcanic areas. Sasa nipponica lower unit of this community occurs in the granitic area, Cacalia yatabei lower unit occurs on steep mountain slopes consisting of mudstone, and Carex reinii lower unit occurs on the area of Tertialy greentuff. The Species composition of Abies homolepis forests in this area is affected by climate and geology, because volcanic activity or active faulting along the Itoigawa-Shizuoka Tectonic line in Fossa Magna created remarkable features and disturbances, and Abies homolepis growing on rocks and unfertile soil in this area are influenced by mother rocks