Effect of litter species and topography on litter quality and decomposition rates in central Himalayan region

Leaf litters from Oak (Quercus leucotrichoflora), Angyar (Lyonia ovalifolia), Melu (Pyrus peshia), Burans (Rhododendron arboreum) and Chir (Pinus roxburghii) were collected from north facing site and south facing site and at three slope positions (top, middle and bottom) on each aspect that had similar soil chemical characteristics (soil pH, Organic C and total N). The litters were analysed for initial carbon, total nitrogen, lignin, cellulose and polyphenol concentrations. Litter carbon, nitrogen, C: N ratio, lignin and lignin: N ratio varied significantly within and between species at different aspect and slope positions. Litter decomposition was studied in the field using litter bag technique. The litters were placed on two aspects and at three slope positions and were sampled every 90 days for a total of 410 days. The main effects of aspect, species and slope position on decomposition rates were all statistically significant. Oak leaf litter showed highest decomposition rates followed by Lyonia, Pyrus, Rhododendron and Pinus. The litters placed on north facing site decomposed faster than at those on the south-facing slope. The litters placed on top slope position decomposed slower than those at either middle or bottom slope position. Initial lignin concentrations explained most of the variation in decomposition rates between species and within species for the aspects and slope positions. The result shows that litter quality has the potential to define the rates of microbial decomposition however they are significantly affected by the biotic and abiotic environment in which the decomposition takes place.