Litter of multipurpose trees in Kerala, India: variations in the amount, quality, decay rates and release of nutrients

In a field study involving 8-9 year-old woodlots of nine fast growing tree species in Kerala, India, the amount and nutrient content of litterfall were monitored. Decay rate constants and litter half-lives were estimated by fitting a single exponential model to the litter decomposition data. Annual litter production ranged from 3.43 Mg ha(-1) (Pterocarpus) to 12.69 Mg ha(-1) (Acacia). Litterfall of Acacia, Ailanthus, Pterocarpus and Casuarina followed a uni-modal distribution pattern. Nutrient content of litter samples showed considerable variations, owing to species and sampling time. Based on mean litter N content, the nine species were broadly divided into high, medium and low detrital N species. Litterfall accounted for substantial nutrient recycling within the system. Results of the litter bag study revealed that residual litter mass declined exponentially with time for Ailanthus, Pterocarpus, Casuarina and Leucaena. Paraserianthus showed a linear trend, while Emblica and the two Artocarpus species exhibited a bi-phasic pattern of mass loss. Both initial lignin content and lignin-N ratio had a negative, although modest influence on decay rate coefficients, while initial N content exerted a positive influence. Nutrient release from the decomposing litter followed either a tri-phasic pattern characterised by an initial accumulation, followed by a rapid release and a final slower release phase, or a bi-phasic pattern that is devoid of the initial accumulation phase. (C) 1999 Elsevier Science B.V. All rights reserved.