森林立地54(1),19〜28 2012

Jpn J For Environ 54 (1), 19–28, 2012

 

放置期間の違いが竹林の下層植生の発達に与える影響

 

小谷二郎¹・江崎功二郎^１

^１石川県林業試験場

 

成立過程や放置してからの期間の異なる3地域の竹林（モウソウチク林）で，下層植生と埋土種子を比較した。過去にタケノコ生産を行い放置してからの期間が短い竹林での下層植生の種数や被度および高木の密度は，侵入拡大によって長期間放置された竹林よりも高い値を示した。下層植生が比較的に豊富に残っていた竹林での木本の種数や密度は，この周辺の広葉樹二次林での植生よりも必ずしも少なくなかった。3地域間での埋土種子の種構成は異なったが，どの竹林も先駆種を多く含んでいた。また，埋土種子の種数や密度は地域間で差はみられず，周辺スギ人工林よりも多い傾向がみられた。以上のことから，放置してからの期間の短い竹林では広葉樹二次林やスギ人工林と同等な豊富な植生を潜在的に保有しているものと考えられた。

キーワード：下層植生，放置期間，放置竹林，埋土種子，モウソウチク

 

Jiro Kodani and Kojiro Esaki：Effect of the duration of abandonment on development of understory vegetation in bamboo forests. Japanese Journal of Forest Environment 54:19−27, 2012.

We compared the understory vegetation and soil seed bank in three areas of the bamboo (Phyllostachys pubescens) forests which have different process of formation or duration of abandonment. The number of species and/or coverage of understory and the tree density in the bamboo forests abandoned for a shorter period were higher than those in the bamboo forest abandoned for a longer period due to the invasion and growth. The species richness and coverage of trees in bamboo forests where understory vegetation remained relatively rich was not always lower than those in the broad-leaved secondary stands. The species compositions of soil seed bank were different among three areas of the bamboo forests, but the all forests contained many pioneer species. The number of species or the density of buried seeds in bamboo forests were not different among three areas, and tended to be richer than those in surrounding Cryptomeria japonica plantations. As a result, the bamboo forests abandoned for a shorter period is considered to have potential for maintaining the same rich vegetation as broad-leaved secondary forest or C. japonica plantations.

Key words : abandoned bamboo forest, duration of abandonment, Phyllostachys pubescens, soil seed bank, understory vegetation