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Revegetation of gold residues in the eastern jarrah forest in the south-west of western Australia
Conference paper   Open access

Revegetation of gold residues in the eastern jarrah forest in the south-west of western Australia

W. McGrath, R. Bell, D.A. Jasper, C. Hinz, I. Struthers, J. Eastham and P. McNeil
ASMR
2003 National Meeting of the American Society of Mining and Reclamation and The 9th Billings Land Reclamation Symposium (Billings MT, USA, 03/06/2003–06/06/2003)
2003
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Abstract

Revegetation of mine residues (tailings) is an important aspect of rehabilitation after mining, and represents a substantial investment. Therefore it is important to increase our understanding of all aspects of re-establishing a sustainable vegetation community on these materials. We report here on a multi-disciplinary, collaborative research program, focusing on vegetation establishment, soil development, and water-balance modeling on a large residue revegetation experiment. The study focused on gold residues produced at the Boddington Gold Mine (BGM) and Hedges Gold Mine (HGM), in the south-west of Australia. The residue storage areas will be rehabilitated once no longer required, but revegetation may be hampered by the alkaline, saline, and sodic properties of the residue. A large field experiment was established to examine soil amendments and capping strategies. The treatments were three depths of gravel-rich subsoil (0 cm, 15 cm, and 30 cm) overlying residue treated with gypsum (30 t/ha). All plots subsequently received an application of topsoil (10 cm). The plots were established in 1999 with species from the local jarrah (Eucalyptus marginata Donn. ex Smith) forest, or salt- and waterlogging-tolerant native species. Ten months after application, gypsum had contributed to a decrease in residue pH and salinity. By March 2000, approximately 90% of the directly seeded species had emerged and survived, and 100% of transplanted seedlings had survived. Applying gravel subsoil in addition to topsoil did not improve plant growth in the first two years. In fact, aboveground biomass production was higher, from 4 to 8.5 t/ha/yr, in the absence of a gravel subsoil. However, in the third growing season, this trend was less apparent. Plant roots were found to grow into the residue, preferentially following shrinkage cracks and exploring coarser-textured layers. Vigorous plant and root growth, and thus high plant water use, has resulted in substantial drying of the residue profile. On-going studies are examining water and salt movement through these profiles and long-term plant performance. At the same time, an overall model is being developed to predict the net water balance if the whole residue area was vegetated.

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