A comparison of the vegetation communities from the islands of the Pitcairn Group

Abstract

Abstract The vegetation of the raised coralline Henderson Island and Oeno Atoll (Pitcairn Group, south-central Pacific Ocean) is described from cover-abundance values of the vascular flora sampled in 10 10 m quadrats. Exploratory data analysis by detrended correspondence analysis and two-way indicator species analysis was used to summarize the resulting data matrices for each island, and to aid definition of vegetation types. For Henderson, six major vegetation communities are described, which are often closely linked to geomorphology: beachfront, embayment forests, open limestone scrub, cliff and ledge, exposed cliff top, and plateau forests. For Oeno, four main vegetation communities are described: open sandy littoral,Argusiascrub, closed forest, and coconut grove. For each island, the main vegetation types were further subdivided into a number of communities depending on the proportions of various taxa. Brief qualitative descriptions of the vegetation of Ducie and Pitcairn are also given. Anthropogenic communities, some of which are highly invasive, are widespread on Pitcairn. Adequate conservation measures must be given to all islands in the Pitcairn Group; this will protect not only the endemic-rich and possibly unique plateau forests of Henderson, but also the species-poor and scientifically important analogues of vegetation types which occur elsewhere in the Pacific islands.