ENVIRONMENTAL CORRELATES OF TREE SPECIES DIVERSITG IN STAGE-III OF KAKADU NATIONAL-PARK, NORTHERN AUSTRALIA

A quadrat based survey (n = 380) that sampled across the environmental range of the geologically and topographically diverse Stage III of Ka kadu National Park, Northern Territory, revealed that the region has a tree flora dominated by the family Myrtaceae, and the genus Eucalyptu s in particular. Principal components analysis (PCA) defined three axe s of environmental variation: site rockiness, site hydrology and surfa ce soil clay content. The three PCA axes were divided into halves and a 2 x 2 x 2 matrix was created to classify eight environments; however , there were quadrats in only seven of the eight possible environments . Kruskal-Wallis one-way ANOVAs showed that there was significant vari ation of the following variables between the seven environments: total basal area, tree species richness, proportion tree richness composed of eucalypt species, and proportion of eucalypt richness composed of t he four subgenera Blakella, Corymbia, Eudesmia and Symphyomyrtus. Of t he most abundant 25 tree species and other common eucalyptus only five species (Allosyncarpia ternata, Eucalyptus bigalerita, E. clavigera, E. foelscheana and E. jacobsiana) did not have significant differences in their mean basal area between the seven environments. The above pa tterns are interpreted as evidence that the savanna is a highly evolve d system rather than the product of geologically recent disturbance to a once widespread monsoon rainforest.