Leaf-litter decomposition in an oak-conifer forest in Himalaya: the effects of climate and chemical composition

Abstract

The decomposition rates of certain dominant litter species in an undisturbed oak-conifer forest in the Kumaun Himalaya were investigated by enclosing pre-weighed, newly senesced leaves in litter bags, placing these bags on the forest floor and determining the weight loss by recovering the bags at monthly intervals. Among the species examined, Daphne cannabina decomposed fastest and Cupressus torulosa decomposed most slowly. The former took 6 months for complete decomposition, while Cupressus torulosa decomposed to about 72 per cent in 18 months. A linear combination of rainfall and temperature explained 80 per cent of the variability in monthly weight loss. The rate of decomposition was also related to the initial chemical composition of the litter. Initially, several constituents showed a significant relation with decomposition; these are nitrogen, calcium, water soluble compounds, total nonstructural carbohydrates, lignin, acid detergent cell wall components and fibre. Of these, lignin and fibre contents showed a negative relation with weight loss while the others were positively related. As decomposition progressed, only nitrogen, lignin, ADCW and fibre content remained important. With further lapse of time only two constituents, nitrogen and lignin, remained important. Among these the effect of nitrogen declined with time while that of lignin increased. A linear combination of nitrogen and lignin explained 59 per cent variability in the annual weight loss.