Characteristics And Responses To Changes In Environmental Conditions Of Litter Decomposition In Plant Species Of Stipa Krylovii Roshev. Steppe

Litter decomposition plays an important role in nutrients recycling. In this study, we examined several key processes and problems associated with litter decomposition in a semi-arid Stipa krylovii Roshev. grassland ecosystem in an agro-pastoral ecotone of northern China. The major subject areas include the decay rates and nutrient dynamics in litters of several common plant species, the occurrence of litter mixture effects (i.e. non-additive effects) and its underlying mechanism, the effects of increased precipitation and soil available nitrogen (N) and phosphorus (P) induced by global change on litter decomposition and net carbon (C) storage of grassland ecosystem.The litter decomposition rate was studied in several species, including Stipa krylovii Roshev., Cleistogenes squarrosa Trin., Allium bidentatum Fisch., Allium ramosum L. Sp. Pl. and Agropyron cristatum Gaertn.. Results showed that the decomposition rates of leaves and stems were significantly and positively correlated with initial litter N and P concentrations. The decomposition rates of fine roots were significantly and negatively correlated with initial litter C/N ratios. Roots generally decomposed faster and had faster nutrient turnover rates than leaves and stems. Mixture effects (i.e. the deviation of litter mixture decomposition rates from the expected values based on the composite single litter) were found in some of the litter mixtures. The litter mixture effects resulted in overall nutrient (N, P, Ca and Mg) immobilization or delayed nutrient release. The occurrence and mode of mixture effects were dependent of the characters of component litters and had no obvious correlations with litter diversity.