Alcoa World Alumina Australia has been rehabilitating bauxite mines in the jarrah forest of Western Australia for more than 35 years. An experiment was established in 1988 using three different seed treatments (legume and small understorey mix, small understorey mix only, and no seed) and two fertilizer treatments (N and P, and P only). The objectives of this study were to (1) document vegetation changes in the first 14 years after bauxite mining; (2) assess whether the vegetation is becoming more similar to the unmined forest; and (3) gain a better understanding of successional processes. Seed treatments significantly affected 13 of the 14 measured vegetation characteristics. Native species richness was higher in seeded than in unseeded sites at 1, 2, and 5 years of age, whereas diversity and evenness were generally higher at all assessment ages. Exotic species density was higher in unseeded than in seeded sites from 5 years onward, whereas richness was higher from 8 years onward. Nitrogen fertilizer significantly increased exotic species richness, density, and cover. Ephemerals dominated plant density in all rehabilitation treatments over time, whereas seeder species dominated cover. In contrast, resprouting species dominated density and cover in the unmined forest. Orchids were the only species that were not present in the first year in rehabilitated sites but increased in abundance over time. Vegetation composition in rehabilitated areas did not become more similar to the unmined forest during the 14 years since seeding, instead strongly reflected the initial species mix. Rehabilitated bauxite mines appear to follow the initial floristic composition model of succession.

A critical aspect of reestablishing a self-sustaining Jarrah (Eucalyptus marginata) forest ecosystem to bauxitemined areas is to ensure that vital ecosystem functions such as litter decomposition and nutrient cycling are returned. Significant research has been undertaken over the past 20 years relating to litter decomposition and nutrient cycling. Studies have shown that litter accumulates rapidly in restored areas (1-4 ton ha 21 yr 21 ) and the accumulated litter tends to be richer in nitrogen due to intentionally elevated densities of nitrogen-fixing species. This leads to a lower (carbon:nitrogen) C:N ratio (60:1 compared to 130:1 in unmined forest) that may promote mineralization of organic N to inorganic forms in restored areas. The major nutrient store in the unmined forest is in the soil and returning soil during the restoration process largely conserves this resource, particularly in relation to P.Short-term plant macronutrient requirements for growth are readily restored by fertilizer application. Studies on the reaccumulation of nutrient pools in the successional development of restored areas have shown that pools equivalent to the unmined forest are established within 10-20 years. Ongoing research is focusing on the rates of cycling processes in burnt and unburnt restored areas, and comparing these to the unmined forest to ensure that key functions have been reestablished. To date, all measured ecosystem function parameters are indicating that restored areas have achieved or are on a trajectory toward a self-sustaining Jarrah forest ecosystem.

We studied the effects of soil handling operations during bauxite mining and restoration on the numbers and depth distribution of seed stored in the surface soil of the jarrah forest. Germinable seed stores were determined in four sites of undisturbed forest, these same sites after clearing and burning of forest residues, in the soil immediately following the construction of topsoil stockpiles, in the respread topsoil and then after deep ripping of the respread topsoil. Average density of germinable seed at four sites prior to disturbance was 352 m−2. After clearing and burning, the seed store had decreased to a mean 74% of the original forest soil seed store density. When the top‐soil was stockpiled prior to respreading, the seed content was further reduced to 31% in freshly constructed stockpiles and had declined to 13% after 10 months in the stockpiles. After ripping of the respread topsoil the seed content was 16% of the original forest seed store density. In one site where the topsoil was directly stripped and respread with no period of stockpiling but with a period of fallow, the seed store was 32% after respreading and then increased to 53% of the original forest store after ripping. This increase may have been caused by an underestimate of the reserves due to insufficient heating of the samples to break dormancy in fire‐requiring species. In the forest topsoils seed was concentrated in the upper few centimeters of the soil profile, whereas after the mining and restoration operations seed was evenly distributed throughout the returned soil profile to a depth of 20 cm. Small‐seeded annual species, which were common in the forest seed store, were more sensitive to the soil handing operations and declined to very low numbers, whereas hard‐seeded plant species such as Acacia spp. were less affected by the soil handling operations. Implications for bauxite mine revegetation operations include the recommendation that direct return of topsoil should be carried out wherever possible with a minimum delay between clearing, stripping, respreading, and ripping.

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Germinable seed stores were measured in jarrah forest soils at six sites during one year. The overall mean seed content to a depth of 5 cm was 292 seeds m~-. There was a significant seasonal difference, with a maximum of 435 seeds m~' in summer, after the majority of species in this Mediterranean ecosystem had flowered and set seed, and a minimum of 207 seeds m"-in winter. There were also large site differences in both the densities of seed present and the species represented in the soil seed store. More than 85 species were represented in the germinable seed store firom a total sampling area of 17.28 m^. The germination oi Acacia drummondii, Acacia pulchella, Bossiaea aquifolium, Kennedia coccinea, Lasiopetalum floribundum and Trymalium ledifolium were significantly increased by heating the soil. Smoke produced a significant positive germination response in one species {Trymalium ledifolium). To maximize the contribution of the soil seed store to mine rehabilitation, the ideal revegetation sequence is to collect the topsoil immediately after clearing the vegetation in summer, immediately return the soil to an area to be revegetated, and carry out all earthmo^ving, landscaping and seedbed preparations prior to the onset of the autumn rains.