Litterfall, litter decomposition and nutrient release patterns in four native tree species raised on coal mine spoil at Singrauli, India

Litterfall, leaf litter decomposition and N and P release were studied in four tree species (Dalbergia sissoo, Azadirachta indica, Pongamia pinnata and Shorea robusta) planted on a mine spoil habitat. Annual litterfall varied from 1220 kg ha(-1) in the S. robusta stand to 3620 kg ha(-1) in the A. indica stand. The fast-growing species A. indica and D, sissoo exhibited higher litter production in comparison to the other two slow-growing species. The total N returned to the soil through litterfall ranged from 8.6 kg ha(-1) year(-1) in the S. robusta stand to 36.5 kg ha(-1) year(-1) in the D. sissoo stand. The annual percent leaf litter mass loss was distinctly greater in A. indica (73%) and D. sissoo (69%) in comparison to P. pinatta (59%) and S. robusta (47%). The mean relative decomposition rates of leaf litter material were maximum in the rainy season and minimum in summer. Rainfall and its associated variables exhibited greater control over litter decomposition than temperature. Lignin and water-soluble compounds were better predictors of annual mass loss rates accounting for 90% variability. Mass loss was positively correlated with N and P mineralization rates. Lignin was the best predictor of annual N and P mineralization rates. Nutrient release pattern differed; constant release occurred in A. indica, initial release followed by delayed immobilization and release occurred in D. sissoo and P. pinnata, and initial immobilization followed by gradual release was noticed in S. robusta. A. indica and D. sissoo, showing high litterfall and rapid litter decomposition rate, hold promise for the rehabilitation of nutrient-poor coal mine spoils. On the other hand, S. robusta with less litterfall and a slow decomposition rate may prove disadvantageous.