小笠原諸島母島においてギンネムの生物学的侵入が二次植生の遷移と種多様性に与える影響
2000 年 50 巻 2 号 p. 111-119
詳細
2000 年 50 巻 2 号 p. 111-119
We surveyed the relationship between the secondary-successional pathway and species diversity in secondary forests that have developed in the 55 years following agricultural abandonment throughout the Southern Region of Hahajima Island, one of the Ogasawara (Bonin) Islands, in the northwestern Pacific. Four forest types (Leucaena leucocephala comm., Bischofia javanica-Morus australis comm., Rhaphiolepis wrightiana comm., and Planchonella obovata-Hibiscus glaber comm.) were distinguished at the second level of the TWINSPAN classification, and differed from each other in the secondary-successional pathway interpreted from several historical aerial photographs. The late-successional secondary forests in areas that were invaded by L. leucocephala (B. javanica-M. australis comm.) differ markedly in species composition and forest structure from those in areas that were not invaded by L. leucocephala (R. wrightiana comm.). Late-successional alien species (B. javanica and M. australis) dominate the former areas and biodiversity is significantly lower, whereas the latter areas are more similar to the remaining natural forests in terms of both species composition and specids diversity. This comparison suggests that biological invasion irreversibly changes the secondary-successional pathway, and decreases the species diversity of late-successional secondary forests.
