Dy Mics in Growth and Survivals of Robinia Pseudoacacia Sprouts Occurred After Cutting Conducted in Different Seasons

27 Mar Dy Mics in Growth and Survivals of Robinia Pseudoacacia Sprouts Occurred After Cutting Conducted in Different Seasons

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Abstract

侵略的外来種ニセアカシアの萌芽力の季節性を明らかにするために, 北海道美唄市内の2林分において, 2004年5月, 6月, 8月に伐採処理を行い, その後の萌芽枝の動態を3生育期間に渡って調査した。最高萌芽枝高は3生育期間を通じて5月伐採区で高く, 8月伐採区で低い傾向がみられ, 同じ伐採時期では盤の沢より南美唄で常に高かった。発生した萌芽枝は時間とともに急速に減少し, 株の枯死は2005年から2007年の間に顕著に進行した。統計解析の結果, 伐採時期は最高萌芽枝高と株の生残に影響し, 株の生残には前年の最高萌芽枝高も影響することが示された。2007年における調査区内の萌芽枝材積は, 8月伐採区で最も小さかった。以上の結果から, 駆除を目的にニセアカシアの伐採を行う場合, 盛夏の伐採が有効であることが示された。

English Abstract

To demonstrate the seaso lity of sprouting characteristics in Robinia pseudoacacia, we investigated sprout dy mics in Bibai, Hokkaido, northern Japan, over three growing seasons after the cutting of above-ground parts in May, June, or August 2004. Treatment season influenced growth in height for three consecutive growing seasons. Height growth tended to be higher for the May treatment and lower for the August treatment. The height growth for the same treatment season was consistently higher in Mi mi-Bibai stand than in Bannosawa stand. The number of sprouts decreased quickly and death of parent stumps, defined as the disappearance of living sprouts, was mainly observed between fall 2005 and spring 2007. Statistical a lyses showed the dependency on treatment season for the sprout height and death of parent stumps. Death of parent stumps was also dependent on sprout height at the previous investigation. The volume of sprouts in 2007 was lowest in the August treatment. These results suggest that cutting the above-ground parts of R. pseudoacacia during high summer is effective for the removal of this alien species.