Restoring a Jarrah Forest Understorey Vegetation after Bauxite Mining in Western Australia

Abstract

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 163 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.

Comparison of translocation methods to conserve metallophyte communities in the Southeastern D.R. Congo

“…TFM is currently experimenting with equipment such as tree spades which are able to salvage deeper soils and obtain more root systems, and thereby increase translocation of the important structuring species. Vegetative reproduction techniques, such as tissue culture used in Bauxite Mines in Western Australia (Koch 2007), may also provide another mechanism for conserving these species. Third, supplemental planting could be used to translocate target species which are not successfully transferred through topsoil spreading or whole turf translocation.…”

Case Study: Some Lessons From the Early Development of Native Forest Rehabilitation at Three Surface Mine Complexes in Australia

“…However, it has often been pointed out that the vegetation established on rehabilitated sites generally differ to varying degrees in their similarity to 'native' target assemblage types (Norman et al, 2006;Koch, 2007b;Herath et al, 2009;Doley, et al, 2012). At the three sites examined in this study, this can largely be explained simply by the fact that a mixture of species associated with several communities and non-typical species have been sown or planted.…”

“…As observed by Koch (2007b), Gravina et al (2011 and Unpublished b), and others such as Mulligan et al (2006), the vegetation subsequently establishing over the 20 or so years of monitoring taken place usually reflects that sown and planted.…”

“…The forest with its variable landscape of ridges and small valleys with swamps and ephemeral streams is regarded as being of the highest international biodiversity importance (Hopper, 2009). Koch (2007b) Table 1 on next page).…”

“…The jarrah forest in Western Australia is a dry sclerophyll open forest to woodland of unusual composition being dominated by a mixture of two eucalypt species, jarrah (Eucalyptus marginata) and marri (Corymbia calophylla), and noted for its varied plant assemblages and diverse flora, particularly in its understory (Koch, 2007b). The forest with its variable landscape of ridges and small valleys with swamps and ephemeral streams is regarded as being of the highest international biodiversity importance (Hopper, 2009).…”