Notes on the vegetation of the Bougainville Peninsula,Osborn and Institut Islands,North Kimberley District,Western Australia

The Bougainville Peninsula is formed of basalt capped with mesaform remnants of a bauxitic duricrust. On the plateau so formed there is little soil and the vegetation comprises scattered stunted eucalypts with grasses and hummock grasses or an understorey of Acacia and other shrubs. Locally there are patches of woodland of Eucalyptus nesophila and E. miniata. On the basalt country below the plateau there is deciduous vine thicket in the less accessible parts, a patchy mixture of vine thicket and savanna elsewhere including communities of vine thicket with scattered emergent eucalypts. The Osborn Islands are similar except that the mesaform capping is generally of sandstone. It is concluded that fire is the principal factor regulating the balance between vine thicket and savanna. Up to 40 years ago the area was populated by aborigines and regularly burnt off but this has now ceased so that colonisation by vine thicket is in progress, in spite of the low rainfall of the area.These authors are indebted to the Amax Exploration Company for providing helicopter transport to the localities concerned and for approval to publish this paper: also to the staff of the Western Australian Herbarium, Mr M. I. Brooker, Mr J. Macorochie and Dr V. Semeniuk for the identification of botanical specimens.This author is indebted to the Department of Defence (Navy Office) for permission to join a naval patrol boat. The assistance of Lieutenants J. Wells, R. Gates and the crew of HMAS Attack is gratefully acknowledged. The co-operation of Mr T. P. Farrell (CRA Services) and the Mitchell Plateau Bauxite Company for providing helicopter transport is also appreciated.