Effects of nitrogen deposition and drought on litter decomposition in a temperate forest

To study the responses of nitrogen (N) deposition and drought on litter decomposition, we conducted an in situ experiment in a broadleaf-Korean pine mixed forest in Changbai Mountains by using litterbag technique. Four treatments were installed, i.e., null level of N (CK), N addition (N, 50 kg N/(ha·a)), precipitation reduction (RP, -30%) and precipitation reduction combined with N addition (RP+N). The results showed that it would take 6.025 to 15.167 years to decompose 95% of mass of litter used. Among the tree species, Tilia amurensis (TA) had the highest decomposition rate, followed by Quercus mongolica (MQ), and Pinus koraiensis (PK) showed the lowest decomposition rate. After 92 d and 154 d, although the litter decomposition rate with N addition was higher than those with CK, no significant difference was found, whereas the decomposition rate of litter in RP and RP+N treatments was significantly lower than that of CK (P<, 0.05). But after 365 d and 457 d, the differences between RP, RP+N and CK were also significant. Compared with CK, N and drought treatments had a 42.64%-51.01% decrease of litter C/N ratio. As a whole, N deposition had no significant effects on litter decomposition and C and N concentration, but RP and RP+N significantly inhibited the litter decomposition, and C and N release.