京都大学芦生演習林における天然生林の植生について

Abstract

1. 京都大学芦生演習林の植生をWhittakerの環境傾度分析に準じて分析した。2. 本地域は海抜高差で500m程度の巾をもつにすぎないが, 温帯落葉樹林帯の代表であるブナの下限と温量指数からみて, 約600mを境として温帯落葉樹林帯と暖帯落葉樹林帯とに区分しうる。ただし, 600mを境として交代するのはブナとウラジロガシ, ミズナラとコナラなど少数に限られ, 大多数の種はほとんど全域に分布する。3. 乾湿度勾配に対応して種はそれぞれ特有の二項分布型の分布曲線を示す。ピークの位置, 曲線の型は種によってそれぞれ違い, 相互に広く重なりあっている。それ故, 植生は湿性から乾性に向って環境の変化に対応して連続的に変化していく。4. 分布曲線のピークが違うことは種のスミワケを示すが, 同時に相互に重なりあい, トモズミの関係を示す。このことから, 森林は個体―環境系の連鎖として成立しているものだといえる。5. 下層の種もまた乾湿度勾配に応じて連続的に変化しており, 上層木との組合せもまた環境の変化に対応して連続的に変化する。6. 少数の種ないし陽性の種の存在様式からみて, 天然生林はモザイク状, 部分的に破壊と再生を含む動的平衡系である。7. 高木の優勢な種に注目すれば, 水分環境に対応して, 最も湿った側から, トチ, ブナ, スギをそれぞれ代表とするグループと最も乾性のネジキ, クロソヨゴ, ヒノキ, ヒメコマツッを主とするグループに分類できる。本地域では海抜700mをこえると準平原地形となり, 弱乾性のスギを代表とするグループの占める割合が多くなる。

1. The study on the vegetation of natural forest was conducted in Kyoto University forest located at Ashiu (Kyoto Prefecture). 2. The elevation of the area ranged from 350 to 950 m in altitude, and cover about 4000 ha. About a half of the area is covered by climax natural forest. In view of vertical distribution, it can be divided into two forest zones, that is, the warm temperate deciduous broad-leaved forest below 600 m altitude, and the cool temperate deciduous broad-leaved forest above 600 m. The boundary was decided based on the lower limit of distribution of Fagus crenate and the warmth and coldness index. But the boundary is significant for only few species such as Fagus crenate, Cyclobalanopsis salicina, Quercus serrata and Quercus mongolica var grosseserrata. Many of tree and shrub species distribute almost every elevation. 3. When the stands were arranged in the order of moisture gradient, all species were found to form binomial curves of occurrence, and curves for different species overlap broadly, but peaks for species and limits of their distribution were well scattered along gradient. Consequently, the stands formed continuous series, and there were no distinct groups of species which could be differentiated from other groups on the basis of floristic composition. It is presumed that each of tree and shrub species distribute essentially independently, and the forest stand is organized as a complex chain of individual tree-environment system. 4. The distribution pattern of shrub species growing as understory was quite similar to that of overstory tree species. There was no distinct evidence that distribution of shrub species of understory were unilateraly regulated by overstory tree species. 5. Climax forest include some intolerant species though low in their population. It would be concluded that the climax forest is the system in dynamic equilibrium including destruction and regeneration in locally or mosaicly. 6. It is able to classify the vegetation in this area into several types on the basis of dominant species. On mesic site, the group represented by Aesculus turbinata; on submesic site the group represented by Fagus crenata; on subxeric site the group represented by Cryptomeria japonica; on xeric site the groups represented by Lyonia ovalifolia var. elliptica, Ilex sugeroki subsp. longipedunculata and Chamaecyparis obtusa, Pinus parviflora. The peneplain develope above about 700 m in altitude in this area, and the percentage of occurence of subxeric group is increase at higher part of the area.