An investigation of the factors governing the distribution of savanna plant communities in northern Australia with particular reference to geology and bedrock mineralisation

Abstract

An investigation was made into the factors governing plant distribution in two areas containing lead-zinc and in one case, copper, mineralisation in Northern Australia.
The distribution of the major units within the savanna vegetation of the study-areas appears to be largely controlled by edaphic and drainage factors. Distinct plant assemblages are developed over the oredeposits. Although the assemblages are restricted to these environments, the individual species also occur in regions apparently devoid of mineralisation. In the area containing both lead-zinc and copper deposits, the same assemblage occurs on both types of mineralisation. The assemblage species are apparently better adapted to withstand higher concentrations of ore-metal in the substrate, and to absorb greater quantities of these metals, than the more widespread plants.
Zinc, copper and lead occur in decreasing order of abundance in plants from un-mineralised localities. Plants growing over the ore-deposits can absorb large quantities of all three metals, but the distribution of metal within the aerial parts varies. In some species, an increased rate of absorption of lead and copper occurs when the plants are growing on soils rich in these metals compared with their rate of absorption elsewhere. This may be related to intra-specific variations within the plants.