Search

ブナの分布を低山地帯において地質の違いから検討した．埼玉県外秩父山地に位置するブナ分布地において現地調査を行い，ブナ個体と基盤岩，傾斜，土壌の分布を図化した．この結果，ブナは秩父中古生層(チャート，砂岩など)と御荷鉾緑色岩類(変斑レイ岩)の急峻な斜面上部にのみ分布した．その他の御荷鉾緑色岩類(変玄武岩類と火山性砕屑岩)と三波川結晶片岩類は，緩やかな斜面上部を形成し，ブナは分布しなかった．秩父中古生層と変斑レイ岩は，急峻な地形を形成する作用から斜面上部では薄い土層となる．しかし撹乱の少ない安定した地表であるため，極相樹種であるブナの分布が可能となる．この地域の優占樹種となるミズナラやコナラは侵入せず，ブナは個体サイズが大きく寿命が長いことから優占できると考えられる．ブナが低山地帯において種として分布できる要因は，基盤岩によって地形がコントロールされているからであると結論付けた．, Effects of different geological conditions and landform patterns on the distribution of Fagus crenata were investigated in the lower montane forest zone. The distribution of vegetation and surrounding environmental conditions of the F. crenata habitat in the Sotochichibu Mountains, central Japan, were mapped by field surveys. F. crenata trees were distributed only on the steep upper slope in the Chichibu Paleo-Mesozoic area (e.g., chert and sandstone) and the Mikabu greenstone area (e.g., metagabbro). No F. crenata trees were distributed along the gentle upper slope in the Mikabu greenstone area (metabasalt and pyroclastic rock) and the Sambagawa crystalline schist area. The Chichibu Paleo-Mesozoic and Mikabu metagabbro areas had a region of thin regolith especially in the steep landform of the upper slope. F. crenata, however, thrive on these bedrocks because of minimal disturbance and a stable regolith region in the upper slope. Moreover, F. crenata has a tendency to invade the habitat of the local dominant species (Quercus crispula and Q. serrata) in the upper slope, during drought conditions. The predominance of F. crenata trees can be ascertained by factors such as individual size and greater longevity in the plant community inhabiting this region. For this reason, we concluded that the F. crenata population can attain a metapopulation level because of the effects of different geological conditions and landforms on its distribution in the lower montane forest zone., 論説