Dynamics and weight loss of leaf litter in central Himalayan forests: Abiotic versus litter quality influences

Abstract

(1) Decomposition of ten Central Himalayan forest litter species was studied for two years to examine: (i) the temporal changes in nutrient concentration and weight loss and its spatial patterns; and (ii) to develop a regional model of litter weight loss based on the dual controls of climate and substrate quality. (2) The experiments involved five forest communities in an altitudinal gradient, each with distinct vegetation and soil. In addition, a standard leaf litter was placed on the forest floor of each of these forests. (3) Litters high in cell wall constituents tend to be lower in nutrient concentrations. Relative patterns of change in K and Ca concentrations tended to differ from those of N, P and Na. (4) Monthly rainfall could account for 25-89% of monthly weight loss of litter on each site. Analysis of the variation in annual weight loss from site to site indicates that the annual temperature, actual evapotranspiration (AET) and altitude explained, respectively, 48.7%, 53.6% and 49.1% of the variability. (5) Measures of cell wall constituents, e.g. lignin concentration, could account for up to 60% of the variability in weight loss in the first year; however, lignin, as a predictor of weight loss rate, contains considerable information about plant nutrients. Linear combinations of lignin, annual temperature and AET/lignin, produced an r² of > 0.78. (6) In warm temperature and subtropical climates the cell wall constituents seem to be good predictors of weight loss in the first year while in cool temperate to arctic climates, the early stages of decay are prolonged, resulting in good prediction by litter nutrients.