CHANGES WITH TIME IN SOIL BIOMASS C, N AND P OF MINE SPOILS IN A DRY TROPICAL ENVIRONMENT
Soil biomass C, N and P were determined for a native forest site, an unmined deforested site and an age-series of adjacent coal mine spoils (5, 10, 12, 16 and 20 yr). Biomass C ranged from 209 to 867 μg g−1 soil, biomass N from 20 to 75 μg g−1 soil and biomass P from 7 to 29 μg g−1 soil. Biomass C, N and P were linearly related to each other. Biomass C was also related to the root biomass. Biomass N with a mean C:N ratio of 11.8 accounted for 2.2–4.2% of the total soil N and was positively related to the mineral N of soil. Biomass C:P ratio ranged from 27.6 to 31.0%. The biomass P was significantly related to the bicarbonate soluble soil Pi. Soil microbial biomass was characterized by a mean C:N:P ratio of 29:3:1. Soil microbial C, N and P were positively related with the age of mine spoils, the values for the youngest spoil (5 yr old) being about four times lower compared to native forest soil. Total soil N was also positively related with age of spoil. The data suggest that microbial biomass can be taken as a functional index of soil redevelopment. Key words: Surface coal mining, soil microbial biomass C, biomass N, biomass P, mine spoil