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シカ排除柵は植生復元に有効な方法であるが, 従来とは異なる植生を生ずることがあり, 十分ではない. 柵を用いた植生復元方法の改善には一時的な柵の開放が有効かもしれない. そこで本研究では, 柵の開放が植生に及ぼす影響を調べるため, 5年前に柵を設置した長治谷草地において柵内外の植生の現状を把握すると共に一時的に柵を開放し, 全種および種ごとの地上部バイオマス量を開放前後で比較した. 柵内ではススキが優占していたが, 先の調査で報告されていた陽生植物は少なかった. 柵外ではイグサに加え, イワヒメワラビが多かった. これらは, 柵内では陽生植物が減少し, 柵外ではシカ不嗜好性植物が増加したことを示唆しており, クラスター解析の結果も柵内外の植生遷移が異なる方向に進んだことを示した. 柵開放の前後に調べた全種の地上部バイオマス量に有意な差はなかったが, オカトラノオ, バライチゴ, ドクダミの地上部バイオマス量は開放後に減少したことが示唆された. したがって, 柵開放に伴うシカによる採食は植生量を減少させるが, 採食は優占種のススキではなくシカ嗜好性の高い種に偏ることを示唆しており, 開放時には嗜好性種の保護にも配慮が必要である., Deer exclosure is not useful enough to restore previous vegetation, because the deer exclosure sometimes result in unexpected vegetation. Temporal opening of the exclosure may be effective to improve the way to restore previous vegetation. We investigated (1)species composition inside and outside the deer exclosure, which was constructed five years ago, and (2)aboveground biomass of total and each species before and after temporal opening of the exclosure at grassland in Japan, to examine the effect of opening of the exclosure on vegetation. Miscanthus sinensis was dominant inside the deer exclosure. Lysimachia clethroides, Potentilla freyniana, and Viola hondoensis were also frequently found but Carex ischnostachya, Hedyotis lindleyana, Agrostis clavata, Viola verecunda, which were frequently found in previous survey, were not. Outside the deer exclosure, Juncus effusus were dominant and Hypolepis punctanta was frequent. These suggest that heliophyte decreased inside the exclosure, whereas non-preferred plants increased outside the exclosure. Results of cluster analysis also support that the succession inside and outside the exclosure have proceeded differently. In temporal opening of the exclosure, aboveground biomass after the opening were significantly smaller than those before opening in three forb species, despite that the total aboveground biomass was not different between before and after opening the exclosure. These results suggested that the preferred species would decrease whereas M. sinensis would be still dominant, if the exclosure was removed for short period. Therefore, protection for the preferred species may be required to open the deer exclosure, to improve the way to restore previous vegetation., 組織改編に伴い2013年より発行元は「京都大学フィールド科学教育研究センター 森林生態系部門」と名称変更

間伐やシカ排除柵の設置を, 立地環境が悪く, 間伐が遅れているスギ人工林において検討した事例は見当たらない. このようなスギ人工林では間伐の効果がほとんどない可能性があり, また, シカ排除柵の設置は下層植生の増加を通じてスギの直径成長を間接的に抑制するかもしれない. そこで本研究では, 間伐とシカ排除柵がスギの定期直径成長量および下層植生の植被率・群落高に及ぼす効果を芦生研究林にある未間伐の40年生スギ人工林で調べた. 間伐試験では, 定期直径成長量は間伐区で有意に大きくなっており, 40年生の未間伐スギ人工林でも間伐は残存木の直径成長を促進することが示された. 下層植生の植被率と群落高は間伐の有無で違いはほとんどなく, 間伐が下層植生の変化を通じてスギの成長に及ぼす影響はよくわからなかった. シカ排除試験では植被率と群落高は柵内で有意に大きくなっていたが, 柵内外の定期直径成長量の違いは認められなかった. 下層植生の植彼率・群落高が大きくなるにもかかわらずスギの直径成長量が抑制されない原因はよくわからなかったが, 少なくとも間伐後3 年目の時点では, シカ排除柵の設置はスギの直径成長を抑制しないことが示唆された., Effect of thinning and deer exclosure on periodic annual increments in diameter of Cryptomeria japonica and vegetation coverage and height were investigated in a 40 years cedar plantation in Ashiu, Japan. We examined whether thinning promotes stem growth of cedars in plantation with delayed thinning on bad growing condition and whether the deer exclosure restrict the stem growth through competition between cedars and understories. In thinning experiment, periodic annual increments in diameter was significantly larger for individuals in thinning plot than those in control plot, indicating that the thinning was effective for a plantation with delayed thinning on bad growing condition to promote diameter growth of cedars. Effect of thinning on vegetation cover and height was not significant in the thinning experiment, and hence, the indirect effect of thinning on the stem growth through understory vegetation was obscure. Deer exclosure significantly increased the vegetation cover and height, whereas the diameter growth of cedars inside fence was not different from that of cedars outside fence. These results show that the deer exclosure does not reduce diameter growth of cedars within three years. However, how the effect of understory on the growth of cedars was reduced remains unsolved., 組織改編に伴い2013年より発行元は「京都大学フィールド科学教育研究センター 森林生態系部門」と名称変更

Effect of thinning and deer exclosure on periodic annual increments in diameter of Cryptomeria japonica and vegetation coverage and height were investigated in a 40 years cedar plantation in Ashiu, Japan. We examined whether thinning promotes stem growth of cedars in plantation with delayed thinning on bad growing condition and whether the deer exclosure restrict the stem growth through competition between cedars and understories. In thinning experiment, periodic annual increments in diameter was significantly larger for individuals in thinning plot than those in control plot, indicating that the thinning was effective for a plantation with delayed thinning on bad growing condition to promote diameter growth of cedars. Effect of thinning on vegetation cover and height was not significant in the thinning experiment, and hence, the indirect effect of thinning on the stem growth through understory vegetation was obscure. Deer exclosure significantly increased the vegetation cover and height, whereas the diameter growth of cedars inside fence was not different from that of cedars outside fence. These results show that the deer exclosure does not reduce diameter growth of cedars within three years. However, how the effect of understory on the growth of cedars was reduced remains unsolved.

Deer exclosure is not useful enough to restore previous vegetation, because the deer exclosure sometimes result in unexpected vegetation. Temporal opening of the exclosure may be effective to improve the way to restore previous vegetation. We investigated (1)species composition inside and outside the deer exclosure, which was constructed five years ago, and (2)aboveground biomass of total and each species before and after temporal opening of the exclosure at grassland in Japan, to examine the effect of opening of the exclosure on vegetation. Miscanthus sinensis was dominant inside the deer exclosure. Lysimachia clethroides, Potentilla freyniana, and Viola hondoensis were also frequently found but Carex ischnostachya, Hedyotis lindleyana, Agrostis clavata, Viola verecunda, which were frequently found in previous survey, were not. Outside the deer exclosure, Juncus effusus were dominant and Hypolepis punctanta was frequent. These suggest that heliophyte decreased inside the exclosure, whereas non-preferred plants increased outside the exclosure. Results of cluster analysis also support that the succession inside and outside the exclosure have proceeded differently. In temporal opening of the exclosure, aboveground biomass after the opening were significantly smaller than those before opening in three forb species, despite that the total aboveground biomass was not different between before and after opening the exclosure. These results suggested that the preferred species would decrease whereas M. sinensis would be still dominant, if the exclosure was removed for short period. Therefore, protection for the preferred species may be required to open the deer exclosure, to improve the way to restore previous vegetation.