The forest in motion : exploratory studies in Western Arnhem Land, Northern Australia

Abstract

As a contribution to academic debate concerning northern Australian vegetation ecology and history, and as a contribution also to contemporary land management issues in that region, the findings of various biogeographical, ecological and ethnobotanical studies are presented here which, collectively, explore the status of monsoon vine-forest (MVF) vegetation in the western Arnhem Land region of the Northern Territory. Structurally, the thesis comprises five papers presented in the chronological sequence of their completion, and a brief, explanatory introduction. The first paper, written early in the field-work programme and presented at a northern Australian symposium focusing on current ecological research in the region, describes vegetation changes associated with the advent of European ecological influence in western Arnhem Land (i·e. within the last 100 or so years), at Giina, a traditional Aboriginal camp-site on the edge of the South Alligator River. The paper describes the elimination of MVF at Giina, qnd its reduction elsewhere in the local area, within the recent, historical past. The paper concludes that the destruction of such vegetation is attributable to feral animal impact and changes to the burning regime. These themes are developed in subsequent papers. Whilst still on field work, and having been approached to present a position paper on MVF in the Northern Territory, the second paper, co-authored with Clyde Dunlop, attempts "to provide an account of the ecology (so far as is known), the condition and the conservation status of monsoon vine-forests in the Northern Territory". This paper challenges the generally

accepted view that the scattered distribution of small, discrete patches of MVF across northern Australia is attributable solely to fragmentation of a former closed forest expanse. On the basis of an ecological survey of MVF patches concentrated on the western Arnhem Land region, but including observations over a wider region of the Northern Territory, it is shown that many

MVF patches occur entirely on landforms developed only in the Holocene (i.e. the last 10 000 years) (e.g. coastal riverine floodplain alluvia, coastal beach ridge deposits). Indeed, 70% of the known Northern Territory MVF flora is observed to occur on such landforms. This paper also provides a review of relevant work undertaken on MVF in the Northern Territory at the time of writing, a description of MVF vegetation Habitat Types, an account of the dependent fauna, a checklist of the known flora, and an assessment of the conservation status of MVF in the region. The third paper, completed at the close of 22 months field studies, was prepared as a consultancy report to the Australian National Parks and Wildlife Service, Canberra. The report details the status, condition, and immediate threats to MVF ecosystems in the vicinity of Kakadu National Park, in the western Arnhem Land region. Special attention is given to the impacts of feral animals, and contemporary and traditional Aboriginal burning practices. The paper also considers the significance of MVF to traditional Aboriginal economy. The final two papers further develop certain themes outlined in preceding papers. The papers present formal analyses of ecological and biogeographical data, relating the findings to

wi1der academic contexts. On the basis of studies concerning the distribution of MVF in the western Arnhem Land region, and the dispersal capacities and biogeographical affinities of component taxa, the fourth paper considers how these observations may contribute usefully to an understanding of the historical status of MVF in that region. The fifth paper is concerned essentially with the current status of MVF, drawing attention to the ecological ramifications of different burning regimes. To place fire in ecological context, this paper first explores the influence of substrate conditions on MVF distribution. These studies indicate that, in the absence of fire impact,seasonally

xeric, oligotrophic substrates are unlikely to limit widespread development of closed canopy, MVF vegetation. Show more