Phosphorus fertiliser placement and seedling success in Australian Jarrah Forest

Natural re-colonisation following surface-mining is often slow and typically requires intervention if the re-establishment of a self-sustaining ecosystem integrated with the surrounding landscape is desired in human timescales. Current rehabilitation practices include an initial application of mineral fertilizer, especially phosphorus, to facilitate good seedling establishment and early ground cover. However, limited evidence suggests long-term effect of an over supply of P may result in disrupted nutrient cycling and the long-term exclusion of P sensitive species. South-west Australian jarrah forests are adapted to inherently low-phosphorus soils due to evolving from low P parent material and subsequent leaching of phosphate. As a result this type of ecosystem has a ‘tight cycle’ of internal redistribution of P in mature ecosystems. The agreed rehabilitation prescription involves ‘scarification’ (soil ripping to a depth of 30-40 cm during January to May) followed by broadcast seeding within 4 days. In August superphosphate (with Cu, Mo Zn) is applied by helicopter. A change from aerial application of fertiliser to a ground-based application at the time of scarification was proposed. To assess the impact of a P fertilizer placement (top-dressed or incorporated) and time of fertilisation (summer, autumn and winter), a large-scale field-trial was established in early 2004 in a post-mined area of Worsley Alumina’s Boddington Bauxite Mine (BBM), Western Australia. This paper evaluates the impact of these treatments on establishment and key growth characteristics of four northern jarrah forest species following the first growing season after field-trial establishment