報告書番号

U98071

タイトル（和文）

森林の再生過程に関する研究 -－亜高山帯林のカラマツとダケカンバによる再生様式－-

タイトル（英文）

Fundamental Study on Regeneration Process of Forests - Regeneration Patterns of Subalpine Forests by Larix kaempferi and Betula ermanii

概要 （図表や脚注は「報告書全文」に掲載しております）

人為的に改変した森林を修復・再生するために必要な基礎的知見を得るため，雪崩の発生年や規模の異なる雪崩跡地が分布する富士山において,雪崩後の再生過程を時系列上で解析した。雪崩跡地の立地条件は雪崩の強度によって４つのタイプに区分できた。強度の攪乱を受けた立地では多数のカラマツが侵入するが，実生の生存率は低く，定着するまでに３～４年かかる。およそ60年経つと，階層構造が未発達なカラマツの一斉高木林が再生されるが，この時になってもシラベの後継樹はほとんど侵入しない。中度の攪乱を受けた立地ではダケカンバの実生が攪乱直後から定着し始め，およそ60年経つと林冠にダケカンバが優占し，下層にシラベの稚樹が優占する林が再生する。弱度の攪乱ではシラベの前生稚樹による再生の進むことが既に明らかになっているので，富士山亜高山帯林の再生様式には攪乱強度に応じた３つの様式のあることが明らかとなった。

概要 （英文）

To clarify the regeneration process of subalpine forests, the regeneration patterns by Larix kaempferi and Betula ermanii on four tracks of snow avalanches that destroyed forests in 1992, 1980, 1938 and 1936 respectively, were investigated on the northern slope of Mt. Fuji.(1) Site conditions on the tracks of snow avalanches Site conditions were classified into four types according to the gradient of disturbance by the avalanches. Type 1 was parts of the track that only canopy layer had been disturbed by the avalanches. Type 2 was similar to type 1, but it was thinly covered with sediment transported by snow from the upper part of the track. Type 3 and 4 were intensively disturbed by the avalanches and they were thickly covered with sediment. The surface soil of the type 3 and 4 showed higher temperature and lower water content than those of the type 1 and 2.(2) Seedling establishment of L. kaempferi and B. ermanii The process of seedling establishment was investigated at each of the sites on the track of avalanche. At type 1 and 2, seedling establishment of B. ermanii began within a year after the avalanche. At type 3 and 4, seedling establishment of L. kaempferi began about three or four years after the avalanche, though mortality of the seedlings was very high in their first winter and in the following summer.(3) Time series changes in regenerated L. kaempferi and B. ermanii communities At the slightly disturbed sites like type 2, B. ermanii shrubs accompanied by other pioneer trees such as L. kaempferi and Alnus maximowiczii regenerated about 20 years after the avalanche. However, pioneer trees had been gradually suppressed by B. ermanii. About 60 years after the avalanche, B. ermanii stands had been dominated and many Abies veitchii saplings, which is a climax species, were found in the stand's understory. At the intensively disturbed sites such as type 3 and 4, only L. kaempferi had regenerated about 20 years after the avalanche and their single-layered stands had developed after 60 years. However, only a few A. veitchii seedlings had emerged in their forest floor. From the above results and our previous reports, it is clear that three patterns of regeneration are found on the track, depending on the gradient of disturbance by the avalanche, as follows: (1) At the intensively disturbed sites, only L. kaempferi regenerates; (2) At the slightly disturbed sites, B. ermanii regeneration dominates; (3) At sites where the forest floor is not disturbed, advanced seedlings of A. veitchii start to regrowth rapidly after the avalanche.

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