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桧山地方における海岸生イタヤカエデ林の林分構造と更新
武田, 展也;夏目, 俊二;宮本, 敏澄;玉井, 裕;矢島, 崇
Permalink : http://hdl.handle.net/2115/44432
KEYWORDS : イタヤカエデ;天然生海岸林;更新;純林;潮風;Acer mono;natural coastal forest;regeneration;pure stand;sea wind
Abstract
北海道桧山地方上ノ国町に成立する海岸性イタヤカエデ林の分布と林分構造及び更新動態を検討した。 イタヤカエデは海岸段丘、海食崖に小面積の純林状林分を形成し、研究対象地における海岸林面積の48.8% を占めていた。調査した3 林分の上層高は、8.3～10.8m で、胸高断面積合計は23.42～30.31 m2/ha であ った。全ての林分でイタヤカエデが胸高断面積率99%以上を占め、中～下層の発達しない一斉林型を呈し た。全上木に占める萌芽由来幹の割合は64.5～84.6%と高かった。林床には大型草本やササ類が密生し稚 樹は少なかった。樹齢階別頻度分布における単幹の分布は一山型に近く、萌芽由来幹のピークとほぼ一致 したが、萌芽由来幹は単幹に比べ広い樹齢階に分布していた。更新は不連続で、機会的に生じた実生更新 とほぼ同時に生じかつ持続的な萌芽更新によって林分が維持されてきたと考えられた。
We investigated the distribution, structure and regeneration process of coastal Acer mono forests in Kaminokuni, Hiyama District, Hokkaido. In the study area, stands of Acer mono accounted for 48.8% of the total forest area. In three stands selected for intensive study, the height of dominant trees was 8.3 to 10.8m, and the total basal area was 23.42 to 30.31 m2/ha. Acer mono accounted for more than 99% of the total basal area in each stand. All stands had unimodal height distribution. The ratio of Acer mono stems that originated from sprouts ranged from 64.5 to 84.6%. Few seedlings were observed on the forest floor of each stand. The age distribution of Acer mono of single stems was unimodal. Peaks in the age distribution of stems of sprout-origin coincided with those of single stems. The difference in age of Acer mono of single stems was small in comparison to that of sprouts. We concluded that trees were regenerated from seeds and vegetative regeneration following a disturbance, and that Acer mono stands are assumed to be maintained by the continuous occurrence of adventitious shoots.
We investigated the distribution, structure and regeneration process of coastal Acer mono forests in Kaminokuni, Hiyama District, Hokkaido. In the study area, stands of Acer mono accounted for 48.8% of the total forest area. In three stands selected for intensive study, the height of dominant trees was 8.3 to 10.8m, and the total basal area was 23.42 to 30.31 m2/ha. Acer mono accounted for more than 99% of the total basal area in each stand. All stands had unimodal height distribution. The ratio of Acer mono stems that originated from sprouts ranged from 64.5 to 84.6%. Few seedlings were observed on the forest floor of each stand. The age distribution of Acer mono of single stems was unimodal. Peaks in the age distribution of stems of sprout-origin coincided with those of single stems. The difference in age of Acer mono of single stems was small in comparison to that of sprouts. We concluded that trees were regenerated from seeds and vegetative regeneration following a disturbance, and that Acer mono stands are assumed to be maintained by the continuous occurrence of adventitious shoots.
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