Response of Betula luminifera leaf litter decomposition to simulated nitrogen deposition in the Rainy Area of West China
华西雨屏区亮叶桦凋落叶分解对模拟氮沉降的响应

Aims Our objective was to determine the effect of simulated increased nitrogen (N) deposition on decomposition of Betula luminifera leaf litter, under a high wet-nitrogen deposition background. Methods From January 2008 to February 2009, a field experiment of simulated N deposition was conducted in a B. luminifera plantation in the Rainy Area of West China. The levels of nitrogen deposition were control (CK), low, medium and high N (0, 5, 15 and 30 g N·m–2·a–1, respectively). A field experiment using the litterbag method was conducted on the decomposition of leaf litter of B. luminifera. In the end of each month, NH4NO3 was added into N-treated plots. Important findings Despite the high background N deposition, there were significant effects of simulated increased N deposition on B.luminifera leaf litter. N treatments significantly slowed the decomposition of B. luminifera leaf litter through inhibiting the decay of lignin and cellulose. The time of 95% mass loss (T95%) of B. luminifera leaf litter was increased by 1.14–1.96 a from 2.65 a (T95% of CK) caused by simulated N deposition. Simulated N deposition significantly increased the remaining amount of carbon, N, phosphorus, potassium, and magnesium after one year of decomposition. However, calcium release rate was stimulated by simulated N deposition in all three N treatments. The initial chemical characteristics of litter determined the response direction of litter decomposition to simulated N deposition, as well as the nutrient release pattern during litter decomposition.