George, SJ, Kelly, R, Greenwood, P & Tibbett, M 2009, 'Is soil carbon being sequestered along a reconstructed biodiverse Australian jarrah forest chronosequence following bauxite mining?', in AB Fourie & M Tibbett (eds), Mine Closure 2009: Proceedings of the Fourth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 137-144, https://doi.org/10.36487/ACG_repo/908_8
(https://papers.acg.uwa.edu.au/p/908_8_George/)
Abstract: Restoring native vegetation and ecosystem processes, such as nutrient cycling, within the soil to pre-mined 
levels is of high priority. Carbon (C) is one aspect of the soil that is affected by the mining and rehabilitation 
process. Soil organic matter is difficult to isolate and measure because of its complexity and heterogeneity. 
Many techniques have been devised to fractionate C into conceptual pools based on their turnover times 
within soil. The measurement of these pools of C can give an indication of the methods of stabilisation within 
an ecosystem. Accumulation, distribution and soil C quality in post-mined rehabilitation was studied at BHP 
Billiton’s Worsley Alumina’s Boddington Bauxite Mine in southwestern Australia and benchmarked to 
adjacent unmined northern jarrah forest soils. The soil profile was analysed to a depth of 20 cm for five 
restored forest age-classes ranging from 2–15 years. The quantity and quality of C in both bulk soils and 
particle-size based discrete C pools showed some positive trends towards convergence with native forest 
levels. Parameters with a fast turnover such as litter layer and labile C pools were most successfully 
returned to pre-mining levels. The litter mass of sites rehabilitated for 15 years marginally exceeded the 
mass of unmined native forest which is attributed to a more productive plant community or decreased 
decomposer activity. C levels throughout the soil profile generally responded well to rehabilitation. The 
more labile (> 200 μm) particulate organic carbon (POC) fraction was returned to comparable native forest 
levels (within significant levels; P ≤ 0.05) at all depth intervals. Even though, the less labile POC fraction 
(200–53 μm) and humus (< 53 μm) fractions showed some evidence of slowly returning towards native 
levels, however, some significant differences were still evident. Floristic analysis showed species 
composition differences between rehabilitated and native forest. As opposed to these parameters, others have 
not yet returned to natural levels – a significant variance of potential concern was the carbon:nitrogen 
(C:N) nutrient ratio for soil depths lower than 2 cm that showed values progressively different from the 
native forest. The labile POC concentrations shows a promising trend which may lead to sequestration of 
more recalcitrant forms of C in the future.