Use of Reclaimed Mine Soil Index (RMSI) for screening of tree species for reclamation of coal mine degraded land

In India forest tree species are commonly used for reclamation of coal mine degraded land, thus selection of appropriate species is essential. Degree of amelioration of rhizosphere mine soil quality by different tree species provides an important guideline for screening of suitable species. Rhizosphere soil samples collected from six common tree species growing in the reclaimed coal mine overburden dumps of Jharia coalfield, Dhanbad, India, were analysed for physico-chemical and biological properties. Principal component analysis (PCA) was employed to derive a Reclaimed Mine Soil Index (RMSI) which was used for ranking of suitability of the species. By using PCA it was found that soil CO2 flux, dehydrogenase activity, organic carbon, soil coarse fraction and moisture content are the most critical properties controlling health of reclaimed coal mine soil. The observed values of the above properties were converted into a unitless score (0-1.00) and the scores were integrated into RMSI. The RMSI values were validated by regression analysis with the plant growth parameters (aerial height, diameter at breast height and canopy cover) for each species. Among the different species growing on the overburden dump, the canopy cover and height was more for Cassia siamea whereas, the diameter was higher for Dalbergia sissoo. Tree species having higher RMSI values could be recommended for reclamation of degraded lands, and could be grouped as: high RMSI (>0.500) - Cassia siamea and Dalbergia sissoo, moderate RMSI: (0.300-0.499) - Leucanea leucocephala, Acacia auriculiformis and Gmelina arborea; and low RMSI (<0.300) - Terminalia arjuna. Based on RMSI it is suggested that C. siamea and D. sissoo are most suitable. Thus tree species growing on reclaimed areas had diverse effects on their respective rhizosphere soil properties, which could directly or indirectly determine the growth and survival of the tree species.