Analysis of soil microbial community level physiological profiles in native and post-mining rehabilitation forest: Which substrates discriminate?

The interpretation of community level physiological profiles (CLPP) may be made ecologically relevant by including carbon (C) substrates that reflect organic molecules likely to be present in a soil. In this study, whole-soil CLPP assays were conducted using 86 C substrates selected firstly on the basis of relevance to soil ecosystems and secondly to provide a range in structural complexity. The impact of mining and rehabilitation on soil CLPP (rehabilitated 3, 13 and 26 years previously) was tested by comparison with adjacent non-mined native jarrah (Eucalyptus marginata) forest soil CLPP. The effect of prescription burning (2 years prior) on rehabilitation and non-mined forest CLPP was also investigated. Our first hypothesis that by 26 years the CLPP of rehabilitation soils would be indistinguishable from non-mined soil CLPP was not supported. Significant differences in CLPP were found between all rehabilitation ages and non-mined forest soil; the extent of differences depending on which substrates were included in the analysis. Conversely, prescription burning was not found to result in any significant differences (P > 0.1) in CLPP of rehabilitation soil (13 year old) or non-mined forest soil. The hypothesis that any differences found in CLPP would be due to greater utilization of more structurally complex C substrates in non-mined soils compared to rehabilitation soils was supported. As a proportion of the total substrate response, non-mined forest soils had a significantly higher response to the group of complex substrates tested. However, a large proportion (up to 37%) of the variation between rehabilitation and non-mined forest soils was also attributable to differential responses to simple organic compounds, in particular the carboxylic acids. The study demonstrated that the discriminatory power and ecological relevance of CLPP was improved through the selection of specific substrates to include in the assay.

► Mining and rehabilitation resulted in long-term shifts in soil CLPP in Eucalypt forest. ► Differential responses were found to complex substrates and simple organic acids. ► Improved CLPP discriminatory power was demonstrated through substrate selection. ► Prescribed burning had no long-term effect on soil CLPP in these forests.