模拟氮、硫沉降对华西雨屏区常绿阔叶林凋落叶分解速率的影响

2013年4月-2014年4月,采用凋落叶分解袋法,研究了华西雨屏区常绿阔叶林凋落叶分解速率对低氮(LN, 50 kg N·hm^-2·a^-1)、高氮(HN, 150 kg N·hm^-2·a^-1)、低硫(LS, 200 kg S·hm^-2·a^-1)、高硫(HS, 400 kg S·hm^-2·a^-1)、低氮低硫(LNLS)、高氮低硫(HNLS)、低氮高硫(LNHS)和高氮高硫(HNHS)沉降的响应.结果表明: 氮、硫沉降1年后各处理的凋落叶质量残留率为57.0%～70.7%,凋落叶分解50%和95%的时间分别为1.47～2.08年和6.33～9.01年;氮沉降对凋落叶分解速率的影响不显著;LS显著提高了凋落叶分解速率,HS显著降低了凋落叶分解速率;LNHS和HNHS显著降低了凋落叶分解速率,LNLS和HNLS对凋落叶分解速率的影响不显著.氮、硫复合沉降对凋落叶分解速率的交互作用显著,且氮沉降与低硫复合沉降间存在拮抗作用,氮沉降与高硫复合沉降间存在协同作用.可见,硫沉降和模拟氮、硫复合沉降影响了华西雨屏区常绿阔叶林凋落叶分解速率,进而影响了凋落叶的分解过程.

Effects of simulated nitrogen and sulfur deposition on litter decomposition rate in an evergreen broad-leaved forest in the Rainy Area of Western China.

To examine the effects of nitrogen and sulfur deposition on litter decomposition rate, a one-year field experiment was conducted with the litter bag method from April 2013 to April 2014 in an evergreen broad-leaved forest in the Rainy Area of Western China. There were nine treatments with three nitrogen levels and three sulfur levels, including control (CK), low nitrogen deposition (LN, 50 kg N·hm^-2·a^-1), high nitrogen deposition (HN, 150 kg N·hm^-2·a^-1), low sulfur deposition (LS, 200 kg S·hm^-2·a^-1), high sulfur deposition (HS, 400 kg S·hm^-2·a^-1), low nitrogen and low sulfur deposition (LNLS), high nitrogen and low sulfur deposition (HSLS), low nitrogen and high sulfur deposition (LNHS), and high nitrogen and high sulfur deposition (HNHS). The results showed that the leaf litter residual rate ranged from 57.0% to 70.7% after one year decomposition. The time of half mass loss ranged from 1.47 to 2.08 years, while the time of 95% mass loss ranged from 6.33 to 9.01 years. Nitrogen deposition had no significant effect on litter decomposition rate. The decomposition rate was significantly increased in LS treatment but significan-tly reduced in HS treatment. The rate was significantly affected by LNHS and HNHS, but unaffected by LNLS and HNLS. In addition, simulated nitrogen and sulfur deposition interacted to affect litter decomposition rate, with antagonistic effects between nitrogen deposition and low-sulfur composite deposition and synergistic effects between nitrogen deposition and high-sulfur composite deposition. In conclusion, sulfur deposition and the combined nitrogen and sulfur deposition affected leaf litter decomposition rate in the evergreen broad-leaved forest, with consequences on the litter decomposition process.