報告書番号

U98062

タイトル（和文）

森林の再生過程に関する研究 -－亜高山帯林のシラベ前生稚樹による再生様式－-

タイトル（英文）

Fundamental Study of Regeneration Process of Forests - Regeneration Pattern of subalpine forests by advanced seedlings of Abies veitchii

概要 （図表や脚注は「報告書全文」に掲載しております）

人為的な環境改変に対する森林の反応および森林の再生技術の検討に必要な基礎的知見を得るため，雪崩の発生時期や規模の異なる雪崩跡地が分布する富士山において,シラベ前生稚樹による再生過程を時系列上で検討した。亜高山帯林が雪崩による攪乱を受けた場合，攪乱前の林床にシラベの前生稚樹が存在し，林床が攪乱されなければ，それら前生稚樹による再生が進む。林冠破壊後，前生稚樹が成長を始めると，それらの空隙には先駆性樹種が多数侵入するが，次第に種間競争が生じ，先駆性樹種は淘汰されていく。およそ80年経つと，シラベだけの単純な林分が形成され，断面積合計ではほぼ極相林のレベルまで達するが，立木密度が高いため，自己間引きが生じている。しかし，群落の構成種や林床状態は極相林とよく類似していた。

概要 （英文）

The regeneration processes of subalpine forests were investigated on the northern slope of Mt.Fuji. The present report aims to clarify the regeneration pattern by advanced seedlings of Abies veitchii on four tracks of snow avalanches that destroyed forests in 1998, 1980, 1921 and 1919 respectively.(1) Survival of advanced seedlings of A. veitchii Most advanced seedlings of A. veitchii survived just after the avalanche of 1998 in the parts of the track that had not been disturbed by the avalanche. A large number of advanced seedlings, especially seedlings smaller than 20cm in height, had been protected by snow cover on the forest floor in the avalanche. These seedlings were expected to accomplish an important role in the regeneration process.(2) Origin of A. veitchii in regenerated communities A. veitchii dominated in the canopies of regenerated communities in the avalanche track 18 years after the avalanche of 1980, were originated from advanced seedlings and their age ranged from 19 to 61 years old. However, pioneer tree species such as Larix kaempferi and Betula ermanii invaded in the gaps between A. veitchii saplings after the avalanche. Also, A. veitchii dominated in the canopies of regenerated forests in the 76- and 78-years old abalanche tracks, were originated from advanced seedlings and their age ranged from 77 to 127 and 79 to 84 years old, respectively.(3) Time series changes in regenerated A. veitchii communities After the destruction of forest canopies by avalanches, it appears that advanced seedlings of A. veitchii start to grow rapidly and a large number of pioneer trees invade the gaps between individual A. veitchii. About 20 years after the avalanches, the tree density was 872/100m2 and total basal area was 0.23m2/100m2. Pioneer trees which invaded in the tracks were reducing by suppression of A. veitchii. About 80 years after the avalanches, single-layered stands of A. veitchii (12m in height) had developed. Its average of total basal area was 0.75m2/100m2 and was almost the same as that of trees in climax stands(0.74m2/100m2). However, tree density (66/100m2) was much higher than in climax stands(10/100m2) and a self-thinning of A. veitchii had occurred during the process of regeneration. From the above results, it is clear that advanced seedlings of A. veitchii regenerate track areas where the advanced seedlings already exist and the forest floors are not disturbed by the avalanches. In the secondary sere by this regeneration pattern, stands of A. veitchii with a high density are regenerated about 80 years after avalanches.

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