Selection of Species Suitable for Derelict Mine Site Rehabilitation in New South Wales,Australia

Approximately 2000 derelict (abandoned) mine sites exist in New South Wales (Australia) from mining and prospecting activities that date back to the mid 1800s. The major objective of this study was to identify a range of native species suitable for use in the rehabilitation of three major derelict mine sites identified in New South Wales namely Howell (Zn, Cu, Ag, Pb), Mole River (As) and Woodsreef (asbestos) through glasshouse pot trials. Waste rock material from each of the three sites was subject to four treatments namely a control, tailings, mulch and tailings/mulch treatment, with 13 species (trees, shrubs and grasses) and four replicates (total of 624 pots).The Mole River and Howell waste rock and tailings provided a similar chemical environment for plants at the start of the experiment (deficient nitrate-N, low pH, high EC) compared to the Woodsreef substrates (deficient nitrate-N, high pH, low available P, high Mg). At the completion of the experiment, Mole River generally had the least favourable chemical environment for plants (highest Zn, Fe, Mn), Howell was intermediate and Woodsreef the best (highest Ca, Mg, pH and lowest metals). Two grass species, Cynodon dactylon and Dicanthium sericeum, exhibited the highest emergence rate (40%), although the emergence of 11 out of 13 species was greater than 12%. In general, mean annual height growth and cover of all species was higher in the mulch and tailings/mulch treatments than the control and tailings treatments. Cynodon dactylon recorded the highest mean annual height increase across the species (66 cm yr^-1), with the tree species,Eucalyptus camaldulensis and Casuarina cunninghamiana, also exhibiting relatively good growth. Mean percentage mortality of all species was generally lowest in the Woodsreef substrate, intermediate in the Howell and highest in the Mole River materials. Mulch treated pots recorded the lowest mortality at all sites. With the exception of Dicanthium sericeum, Aristida ramosa and Casuarina cunninghamiana, mean biomass estimates for all species were significantly higher in the mulch and tailings/mulch treatments compared to the control and tailings treatments. Cynodon dactylon yielded more biomass (mean = 5 t ha^-1) in comparison to the other species. The direct implications of these results to the rehabilitation of derelict mines in the New England Tablelands are also discussed.