Restoring a jarrah forest understorey vegetation after bauxite mining in Western Australia

The Southwest of Western Australia is one of the world's biodiversity hotspots. In the jarrah forest there are at least 300-400 plant species in vegetation that is typically mined and as many as 1163 species per 0.1 ha. Hence, restoring the plant species to post-mining areas is seen as a priority. Approximately 70% of understorey richness is returned via the direct transfer of fresh topsoil. Additions of provenance-correct seeds of between 78 and 113 native jarrah forest species add significantly to post-mining species richness. Many of the broadcast seeds receive a prebroadcast heat or smoke treatment to increase germinability. Approximately 20 additional species are produced by vegetative multiplication or tissue culture and planted into restored areas. Though sequential improvements during the past 30 years, Alcoa now achieves its target to establish in restored areas the same number of native plant species per 80 m(2) as the natural forest. Resampling of permanent plots revealed that species composition of older post-mining areas does not become more similar to unmined forest over one to three decades. Few species (mostly orchids) establish after the first year of restoration and adherence to the initial floristic composition model of forest succession applies to jarrah forest mine site restoration in Western Australia. Alcoa's strategy, therefore, is to maximize the diversity of understorey species in newly restored sites at the first attempt. Future research will investigate methods to further increase the density of the fire resprouter species, a group of species currently under-represented in the restored bauxite mining sites.