The botanical diversity in the Ayawasi area, Irian Jaya, Indonesia

Abstract

In the karst-dominated Ayawasi area (Bird's Head peninsula), the botanical diversity and its relation to soil and geological substratum were studied. An inventory in 22 plots of 0.1 ha was made of all plants (1945) with a dbh ≥ 10 cm (mainly trees). Myrtaceae, Burseraceae, and Euphorbiaceae were the most frequent families (considering relative number of individuals), whereas Myrtaceae, Lauraceae, and Meliaceae were most species-rich. The most frequent genera were Syzygium, Haplolobus, and Lithocarpus, and most species-rich were Syzygium, Garcinia, Elaeocarpus, and Pouteria. The most frequent species were Anisoptera thurifera, Tristaniopsis ferruginea, and Gymnacranthera farquhariana var. zippeliana. Species richness was greater in plots in mixed forest (38–57 species, average 48) than in limestone forest (26–42 species, average 33) and secondary forest (21–46 species, average 34). Some very common species, such as Xanthophyllum novoguineense (Polygalaceae) and Macaranga suwo (Euphorbiaceae), were hitherto herbarium rarities, known from very few collections only. Species dominating earlier investigated forests elsewhere in the Bird's Head Peninsula range from being less important to absent in the presently investigated forest. Explanatory factors for this phenomenon are variation due to the geographical distance, the high beta-diversity of tropical forests in general, habitat differences, and differences in research methods, in particular in their scale.