中文摘要：

森林细根分解是陆地生态系统碳循环的重要过程之一,其分解速率受到大气氮沉降增加的潜在影响.2007年11月至2013年1月,对华西雨屏区苦竹人工林进行每月1次的模拟氮沉降试验,设对照（CK,0）、低氮（5gN·m-2·a-1）、中氮（15gN·hm-2·a-1）和高氮（30gN·m-2·a-1）4个处理.2011年1月起,采用分解袋法研究苦竹细根分解.结果表明：苦竹细根分解呈现出先快后慢的趋势,在分解第1年质量损失达60%,分解第2年质量残留率变化较为平缓.对照处理细根质量损失50%和95%分别需要1.20和5.17a.模拟氮沉降显著抑制了苦竹细根分解,相对于对照,高氮处理细根在分解2a后残留量增加51.0%.模拟氮沉降显著增加了凋落物碳、氮和磷元素的残留率.与对照相比,模拟氮沉降处理4.5a后,中氮和高氮处理土壤pH值显著降低,高氮处理土壤有机碳、总氮、铵态氮和硝态氮含量以及苦竹细根生物量显著增加.

英文摘要：

As an important contributor to carbon （C） flux in the global C cycle, fine root litter de- composition in forests has the potential to be affected by the elevated nitrogen （N） deposition ob- served globally. From November 2007 to January 2013, a field experiment involving monthly simu- lated deposition of N in a Pleioblastus amarus plantation was conducted in the Rainy Area of West China. Four levels of nitrogen deposition were included as control （0 g N·m-2·a^-1 ） , low nitro- gen （5 g N ·m-2·a^-1 ）, medium nitrogen （15 g N·m-2·a^-1 ） and high nitrogen （30 g N ·m-2·a^-1 ）. After 3 years of simulated N deposition experiment （January 2011 ） , a two-year fine root decomposition experiment was conducted in the simulated N deposition plots using litterbag method, under monthly experimental N deposition. The decomposition rates of fine roots were fast first and then slow. Mass loss of fine roots in the first year of decomposition was up to 60% , and the change of the remaining mass was very slow in the second year. The time of 50% and 95% mass loss of fine roots was 1.20 and 5.17 years, respectively, under the conditions of no addition N input. In general, decomposition rates were underestimated using negative exponential model. Sim- ulated N deposition significantly inhibited the decomposition of fine roots. The remaining mass in the high nitrogen treatment was 51.0% higher than that in the control, after two years of decompo- sition. Simulated N deposition increased C, P and K contents in the remaining mass of litter. Com- pared with the control, soil pH decreased significantly in the medium and high nitrogen treatments, soil organic C, total N, ammonium and nitrate contents and fine root biomass of P. amarus in- creased significantly in the high nitrogen treatment after simulated N deposition for 4.5 years.