Evaluation of reclamation success in an open-pit coal mine using integrated soil physical, chemical and biological quality indicators

The evaluation and success of ecological reclamation can be assessed by measuring soil physical, chemical and biological variables, either in isolation or combined into composite indicators. In this study we tested the suitability of biological, chemical and physical quality indicators-and their combination in a General Indicator of Soil Quality (GISQ)-to monitor soil quality in restored areas of an open cast coal mine. These composite indicators were computed with principal component analyses (PCA) and co-inertia multivariate analyses (CoIA). Our biological indicator showed a significant recovery of soil invertebrate communities along the chronosequence. Taxonomic richness increased from 7 taxa the 1st year to 13-17 taxa in 6-20-y sites, far less than in forests (19-20). Soil pH, bulk density and proportion of physical and macro aggregates were highest in the 1-y site, while soil organic matter (SOM), total N and proportion of biogenic aggregates were highest in older sites. In general, the three sub-indicators and the GISQ yielded the lowest values in the 1-y site (from 0.1 to 0.3 on a scale of 0.1 to 1.0), intermediate in the 16- and 20-y sites, (0.4-0.7) and reached highest values in the two forests (0.4-1.0). The GISQ methodology proved efficient in assessing progress in the reclamation process which should not be achieved only by monitoring vegetation cover changes.