Mine soil properties as influenced by tree species and topography of the re-vegetated coal mine overburden dump

Abstract

Re-vegetation or natural succession of plant species is an important factor of soil development in postmining overburden dumps. As the parent material (sedimentary rocks and regolith) is more or less uniform in the dump, the topographic position and vegetation are the major factors that affects the mine soil quality. Accordingly, this study was designed for a relative evaluation of the influence of dump topographical position (crest, backslope, toeslope) and tree species (Azadirachta indica, Cassia siamea, and Leucaena leucocephala) on soil quality. Trees growing on the toeslope of the dump were significantly taller with larger diameter at breast height than those at backslope or crest. Soil moisture, pH, total S, available P, and Fe content were significantly (P < 0.05) affected by topographical position of the dump. All these properties were higher in the toeslope, except S in the crest. Tree species affected all the soil properties, except electrical conductivity and Mn. Organic carbon content was significantly lower for the nitrogen fixer L. leucocephala (2.03 %) than A. indica (3.30 %) or C. siamea (3.39 %). Soil dehydrogenase activity (39.79 mg TPF/24hr/kg) and microbial biomass carbon (286 µg/g) was higher under L. leucocephala, and C. siamea, respectively. Based on redundancy analysis (RDA), 87.5 % of the data variation is explained by the tree species, whereas, only 12.5 % by the topography. Principal component analysis revealed that C. siamea contributes significantly for the variation in soil properties of the dump. Re-vegetated plant species are a dominant factor of soil development in post mining dump than the topographical position. C siamea and the toeslope are closely associated with soil microbial biomass carbon. It is recommended to plant C. siamea with relatively higher planting density in crest and backslope than toeslope of the dump.