ウマスギゴケ群落の構造 : 年齢構成と分布様式

Abstract

ウマスギゴケ群落の維持機構を調べるために, 旧演習林本部中庭のウマスギゴケ群落において, 異なる日射, 乾燥条件下にいくつかのコドラートを設定し, 各調査区毎に刈り取り調査を行なった。より高い乾燥条件下では, 地上茎は短かく葉の密度は高く, 乾燥に対して耐性の高い形状を示した。1年以上の茎は少なく, 当年生の茎のランダムで大量な出芽によって群落は維持されていた。より低い乾燥条件下では, 地上茎は細長く厚いターフを形成し, より高い位置で光合成を行なうような形状を示した。1年生以上の茎は多く, 新茎は過度の集中を避けるように出芽していた。松の木の下ではあまり乾燥せず, 高い日射を得ることができるという極めて好適な生育条件がみられた。そこでは各齢の茎群毎に波状の分布がみられた。これは好適な条件下での高齢の茎の集中的な生き残りと, それによって新しい茎の出芽が抑えられることによると考えた。造精器をつけた雄茎, 胞子をつけた雌茎は主に乾燥があまり強くなく安定した部分に分布していたが, 雌茎は特に古く安定した部分で見られるように思われる。年齢構成, 各齢の茎群の分布様式などについて, 各々が主に分布する群落の聞で差異が見られた。

To investigate the maintenance mechanism of the polytrichum commune community, quadrats and a transect under the different sunlight and dryness conditions were set in the yard of the office of Kyoto University Forest. In each quadrat all shoots are harvested and investegated. In one quadrat under more sunny and dry condition, shoots are short and have dense leaves. In other wards, the form of the individual shoot shows the high tolerance against dryness. The shoots, which are oldr than one year, are comparatively few. But a lot of current shoots come up in a random spatial pattern and keep up the community. In the other quadrats under less dry condition, the shoots grow slim and long. This shows that the photosynthesis can occur at the higher part of the shoot. The older shoots are many, and the current shoots seem to come up in a manner of avoiding the exessive crowding. In a transect under a pine tree, there is very good condition for growth, such as the rich sunlight and less dryness. There, shoot density shows wave like distribution by each age class. This dynamic behavior seems to be resulted from the high rate of survival under good condition and from the suppression of growth of new shoot under the thickly survival canopy. The sexual shoots, that is, the male shoots with antheridum or the female with capusule, are mainly distributed over the stable part of the community under the less dryness. Especially the female shoots seem to develop in the more stably established part of the community. There are some differences in the age structure between the two sexual types.