模拟氮沉降和降雨对华西雨屏区常绿阔叶林土壤呼吸的影响

从2013年12月至2014年11月,通过野外原位试验,对华西雨屏区常绿阔叶林进行了模拟氮沉降和降雨试验,采用LI-8100土壤碳通量分析系统(LI-COR Inc.,USA)测定了对照(CK)、氮沉降(N)、减雨(R)、增雨(W)、氮沉降+减雨(NR)、氮沉降+增雨(NW)6个处理水平的土壤呼吸速率,并通过回归方程分析了温度和湿度与土壤呼吸速率间的关系。结果表明:(1)氮沉降和增雨抑制了常绿阔叶林土壤呼吸速率,减雨促进了常绿阔叶林土壤呼吸速率。(2)减雨使华西雨屏区常绿阔叶林土壤呼吸年通量增加了258 g/m~2,而模拟氮沉降和增雨使华西雨屏区常绿阔叶林土壤呼吸年通量分别减少了321g/m~2和406g/m~2。(3)减雨增加了土壤呼吸的温度敏感性,模拟氮沉降和增雨降低了土壤呼吸的温度敏感性。(4)模拟温度和湿度与土壤呼吸速率间回归方程分析表明,土壤水分对土壤呼吸速率的影响较小。(5)模拟氮沉降和增雨处理减少土壤微生物生物量碳、氮的含量,减雨处理增加了土壤微生物生物量碳、氮的含量。(6)模拟氮沉降和降雨对华西雨屏区土壤CO_2释放的影响未表现出明显的交互作用。

Effects of simulated nitrogen deposition and precipitation changes on soil respiration in an evergreen broad-leaved forest in the Rainy Area of Western China

Nitrogen deposition and changes in precipitation patterns are two primary effects of global climate change. In order to understand the effects of both nitrogen deposition and precipitation changes and their interaction on soil respiration in an evergreen broad-leaved forest, an experiment was conducted in situ in the Rainy Area of Western China. The study included six treatments: a control, nitrogen deposition, water reduction, water addition, nitrogen deposition×water reduction, and nitrogen deposition×water addition. From December 2013 to November 2014, soil respiration rates were measured using the LI-8100 (LI-COR Inc., USA) Automated Soil CO₂ Flux System. The relationships among soil moisture, soil temperature, and soil respiration rate were analyzed via regression analyses. The results indicate that (1) nitrogen deposition and water addition significantly inhibit soil respiration, while water reduction increases the soil respiration rate significantly; (2) water reduction increases soil CO₂ flux by 258 g m^-2 a^-1, while nitrogen deposition and water addition treatments reduced soil CO₂ flux by 321 g m^-2 a^-1 and 406 g m^-2 a^-1, respectively; (3) water reduction increased the temperature sensitivity of soil respiration, while nitrogen deposition and water addition reduced the temperature sensitivity of soil respiration; (4) soil temperature has a greater influence on soil respiration rate than soil moisture; (5) nitrogen deposition and water addition reduced the carbon and nitrogen content of the soil microbial biomass, while water reduction increased the carbon and nitrogen content of the microbial biomass; and (6) the interaction between nitrogen deposition and precipitation changes did not have a significant effect on the soil CO₂ efflux in this forest ecosystem.