盐碱化草地生态系统土壤呼吸对不同氮添加水平的短期响应

Response of Soil Respiration to Different Levels of Short-term Nitrogen Addition in Saline Grassland Ecosystem

为了探讨氮沉降对北方农牧交错带盐碱化草地生态系统土壤呼吸(Rs)的影响,于2017年4月在我国北方农牧交错带(山西省右玉县)盐碱化草地生态系统设置8个不同水平氮添加处理实验(0、1、2、4、8、16、24和32 g N/m^2/y),2017~2018年生长季(5~9月)测定了土壤呼吸的季节变化并分析了土壤呼吸与环境因子的关系。结果表明:(1)土壤呼吸的季节变化呈先升高后降低的趋势,峰值出现在6月底7月初;(2)2017年N8处理下土壤呼吸平均速率显著高于其他处理(P<0.05),2018年N8和N24处理的土壤呼吸速率均显著高于对照和N2处理(P<0.05),其余处理间差异不显著;(3)不同水平氮添加处理下,呼吸速率更多的受土壤温度的影响,土壤含水量次之。因此,在未来全球增温背景下的氮沉降增加会促进农牧交错带盐碱化草地土壤碳的排放,这对全面理解盐碱化草地的重要性和预测全球变化对草地生态系统的潜在影响具有重要意义。

To investigate the effect of nitrogen deposition on soil respiration of saline grassland ecosystem in the agro-pastoral ecotone of northern China, nitrogen addition experiments with eight gradient levels(0, 1, 2, 4, 8, 16, 24, 32 g N/m^2/y) were performed from April, 2017. During the pasture growth season(May to September) from 2017 to 2018, the seasonal variation of soil respiration was determined, and the relationship between soil respiration and environmental factors was analyzed. The results showed that the soil respiration increased first and decreased subsequently with seasonal variation, in which a single peak curve appeared at the end of June and the beginning of July. The average soil respiration rate was significantly higher in N8 treatment group that that of N32 treatment group in 2017(P<0.05). Soil respiration in N8 and N24 treatment groups were significantly higher than that of N0 treatment and N2 treatment groups(P<0.05) in 2018, while no significant changes were found among other treatments. Under different nitrogen addition levels, soil temperature rather than soil water content had more influence on soil respiration rate. Therefore, the increase of nitrogen deposition due to global warming will promote the soil carbon emission of saline grassland in the agro-pastoral ecotone, which is of great significance to fully understand the importance of saline grassland and predict the potential impact of global change on grassland ecosystem.