Response of Ant Community Structure to Understory Removal in a Line-thinned Japanese Cedar (cryptomeria Japonica) Plantation

27 Mar Response of Ant Community Structure to Understory Removal in a Line-thinned Japanese Cedar (cryptomeria Japonica) Plantation

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Abstract

列状間伐を行った兵庫県の47年生スギ人工林において下層植生が節足動物相に与える影響を明らかにするため, 間伐林分および隣接する対照林分において下刈りを行い, アリ群集構造の変化を調査した。アリ類の種数に林分間の差はなかったが, 種構成は異なっており, 間伐林分は広域生息種によって, 対照林分は森林性種によって特徴付けられた。アリ群集構造に対する下刈りの効果は林分間で異なっており, 環境適応性が高く, 撹乱に強い種によって特徴付けられる間伐林分の群集構造は, 下刈りの影響を受けにくいが, 森林環境に特化した種によって特徴付けられる対照林分の群集構造は, 撹乱に対して脆弱であることが示唆された。下刈りがアリ群集構造に与える影響は間伐に比べて小さかったものの, 強度間伐を実施した人工林において林冠閉鎖後も多様な下層植生構造を維持し, 幅広い生育環境を確保すれば, 広域生息種と森林性種の共存が可能となり, アリ類の種多様性が増大すると考えられる。

English Abstract

To elucidate the effects of understory vegetation on arthropod diversity after line thinning, we investigated changes in ant community structure after experimental removal of understory vegetation in a line-thinned stand and an adjacent control stand. There was no difference in the number of ant species found in the two stands. The ant community structure of the line-thinned stand was characterized by habitat generalists, whereas that of the control stand was characterized by woodland specialists. Understory removal affected differently the community structure of the two stands. In the line-thinned stand, the effect may be small because the community was characterized by species with high environmental adaptability, whereas in the control stand, the community, which is characterized by species adapted to closed canopy environments, may be more sensitive to disturbances. Although the effect of understory removal on ant community structure was small compared to that of stand thinning, maintaining a diverse understory following canopy closure after intense thinning may increase ant species diversity by allowing habitat generalists and woodland specialists to coexist.