Change in lignin content during litter decomposition in tropical forest soils (Congo): comparison of exotic plantations and native stands

Fast-growing tree plantations are being extended in tropical countries resulting in new forest ecosystems, the functioning of which is yet not well known. In particular, few data are available concerning lignin decay rate. Lignin, nitrogen and tannin contents of fresh and decaying litter were measured in natural rain forest and in planted stands of Eucalyptus hybrids, Acacia mangium and A. auriculiformis in Congo, together with litter-fall and forest-floor accumulation. Lignin evolution in aging litter exhibited different patterns. Lignin was accumulated under Eucalyptus plantation, but disappeared under natural forest, and was intermediate under Acacia plantations. The relationships with decomposition rates and lignin degradation factors, such as white rot fungi and termites, are also discussed.