Natural colonisation and rehabilitation of a copper smelter desert, Mount Lyell, western Tasmania

This thesis investigates patterns of soil contamination and natural colonisation in an area deforested by a long-established, but decommissioned, copper smelter at Mount Lyell in western Tasmania. The rehabilitation of this area is investigated by modifying colonisation and species performance in relation to edaphic factors in accordance with succession management models. The distribution of soluble metals in soils along transects of increasing, downwind displacement from the smelter stacks provided evidence of Cu/Zn contamination and Al mobilization. A higher than expected soil pH suggested a partial reversal of the process of soil acidification by SO2 deposition. This may, in part, explain relatively low, near-smelter contamination levels at Mount Lyell in comparison to similar sites in the vicinity of smelters of world-renown. Nevertheless, colonising species grown in Mount Lyell soils exhibited severe growth abnormalities and these were linked to elevated water-extractable metal concentrations. A survey of the vascular flora, and multivariate analysis, were used to describe the composition and distribution of vegetation colonising the denuded western slopes of Mount Lyell. Compositional trends were explored in relation to edaphic factors by vector fitting, and a numerical classification of survey sites was used to group sites by characterising species coincidences. The classification was used to describe and map spatially distinct colonising communities that differed demonstrably in their tolerance to the phytotoxic metals present in the soils. Species with differential tolerances to the contaminants were identified. The naturalised, exotic grass Agrostis capillaris, was a wide-spread, metal-tolerant colonising species. In contrast, many local trees and shrubs were intolerant of the extreme site conditions. A strong spatial correspondence was evident between the colonising communities and contamination patterns in the vicinity of the smelter installations. Rehabilitation methods for severely eroded sites adjacent to the original smelters were investigated. Emphasis was placed on broadcast sowing as a means of native species re-introduction. A novel, non-destructive, mechanical seedbed preparation method was compared to a conventional method and was found to provide comparable seedling establishment. Low impact, seedbed preparation and application methods for steep, eroded slopes were also compared and dissimilar methods were found to enhance the establishment of colonising Acacia species. The ameliorative effects of field applications of lime on the growth of colonising seedlings were evaluated. The reclamation of Mount Lyell is discussed with reference to patterns of natural colonisation