Effects of nitrogen addition and water manipulation on leaf litter decomposition

In this study, fivetypes of litter (Pinus koraiensis, Quercus mongolica, Acer mono, Fraxinus mandsurica and Tilia amurensis) and soil of broadleaf-Korean pine mixed forest in Changbai Mountain, northeastern China, were selected to study the effect of nitrogen deposition and water manipulation on the litter decomposition. The results are as follows. The rate of litter decomposition did not change significantly with N addition, but declined when the amount of litter increased. The decomposition rate of Fraxinus mandshurica litter increased with increasing water addition. After 14 weeks of incubation, the N concentration in litter was significantly increased, while the C concentration and C/N ratio of litter were significantly decreased. This phenomenon indicates that both C and N elements in litter may have different migrating patterns. The C and N concentrations of soil increased, the δN value had no significant change, and the δC value and C/N ratio declined after treatment. The δN values of litter residues varied among different water and nitrogen treatments. The δC value of litter residue declined. In addition, there were some interactions among the three factors, i.e. water, nitrogen and litter addition.