原著論文 ORIGINAL PAPER

結実季節の異なる鳥散布植物を利用した自然植生の誘導

高橋一秋¹⁾・ 紙谷智彦²⁾

1)新潟大学大学院自然科学研究科　〒950-2181　新潟市五十嵐二の町8050
2) 新潟大学農学部　〒950-2181　新潟市五十嵐二の町8050

Kazuaki TAKAHASHI¹⁾ and Tomohiko KAMITANI²⁾: Leading the spread of natural vegetation by using bird-dispersed plants of different fruiting season. Ecol. Civil. Eng. 5(2), 179-188, 2003.

1) Graduate School of Science and Technology, Niigata University, 8050, Nino-cho, Ikarashi, Niigata 950-2181, Japan
2) Faculty of Agriculture, Niigata University, 8050, Nino-cho, Ikarashi, Niigata 950-2181, Japan

Abstract:We evaluated whether bird-dispersed tree species, which were planted for landscaping and would be used by birds as perches, facilitated the colonization of bird-dispersed plants beneath them. We compared the composition of both bird-dispersed seeds and plants beneath bird-dispersed perch trees that bore fleshy fruit (summer-fruiting Prunus yedoensis, n=9; autumn-fruiting Sorbus commixta, n=10), wind-dispersed perch trees (Pinus thunbergii, n=10), and a tall grass (Miscanthus sinensis, n= 10) on man-made slopes alongside a road. Seeds that had fallen beneath the 29 perch trees and in the 10 grass sites were collected both in early summer (30 days) and from autumn to winter (150 days) in 39, 1-×1.5-m seed traps made from 0.86-mm mesh polyester cloth. To sample bird-dispersed plants that had colonized sites beneath the perches, four 1-× 1-m quadrats were established in late summer near each of the 39 seed traps. Both the numbers and species of bird-dispersed seeds recorded were highest beneath bird-dispersed perch trees and intermediate beneath wind-dispersed perch trees compared to tall grass. The seed rain was higher beneath bird-dispersed perch trees whose fruiting season overlapped with the fruiting season of the seeds than beneath those did not overlap. Similar trends were also found in the plants surveyed in the quadrats. Thus, bird-dispersed perch trees played an important role in facilitating the colonization of bird-dispersed plants, particularly plants whose fruiting season overlapped with the fruiting season of the perch trees. This suggests that perch trees used in landscaping act as attractive plants to frugivorous birds and can aid in the restoration of natural vegetation.

Key words: bird-dispersed plants, colonization, fruiting season, landscaping, restoration

摘要

道路沿いの盛土法面に緑化木として植栽された鳥散布植物が,鳥散布植物の移住を促進させるかどうかについて検討した.結実季節の異なる鳥散布植物や風散布植物の樹冠下と緑化木が植栽されていない草地に散布される鳥散布種子や出現する鳥散布植物の構成を比較した.対象とした緑化木は,鳥散布植物として初夏に液果を着けるソメイヨシノ(9個体)と秋から冬にかけて液果を着けるナナカマド(10個体),風散布植物としてクロマツ(10個体)とした.一方,緑化木が植栽されていない対照区は,ススキ草地(10ヵ所)とした.鳥散布種子の調査は,各調査木の樹冠下とススキ草地の10ヵ所にシードトラップ(1.5m2,0.86mmメッシュ)を1個ずつ設置し,夏期(30日間)と秋冬期(150日間)に行った.また,植生調査は,各シードトラップに隣接して調査枠(1m2)を4個ずつ設置し,晩夏に行った.
シードトラップに捕捉された鳥散布種子の種数および個数は,ススキ草地よりも緑化木の樹冠下で有意に多かった.同じ緑化木であっても,クロマツの樹冠下よりもソメイヨシノとナナカマドの樹冠下で有意に多かった.緑化木の樹冠下に落下した鳥散布種子の結実季節は,その緑化木の結実季節と有意な重なりを示した.また,植生調査枠に出現した鳥散布植物についても,鳥散布種子の場合と同様な結果を示した.
したがって,鳥散布植物の緑化木は,特に,その緑化木と結実季節が重なる鳥散布植物の移住を促進させることが明らかになった.すなわち,緑化のために植栽された鳥散布植物は,鳥類にとって魅力的な植物であり,目然植生の復元を促進させる植生誘導木の役割を果たしていた.

2002年7月15日受付，2003年1月4日受理
1) e-mail: takahasi@agr.niigata-u.ac.jp