青藏高原高寒草甸氧化亚氮排放特征及其与土壤理化性质耦合关系

Characteristics of nitrous oxide emission from alpinemeadow on Qinghai-Tibet Plateau and its couplingrelationship with soil physical andchemical properties

在青海海北高寒草地生态系统国家野外科学观测研究站,以高寒矮嵩草草甸为研究对象。通过静态密闭箱-气相色谱法,监测生长季盛期高寒草甸N_(2)O排放特征,同时基于路径分析方法,解析土壤理化性质和地上生物量对高寒草地生态系统N_(2)O排放的影响作用。结果表明:生长季高寒草甸N_(2)O排放速率存在较大时间异质性特征,平均排放速率为(39.3±5.4)μg/(m^(2)·h),各月之间均存在显著性差异;土壤理化性质与N_(2)O排放速率之间,可以建立较好的回归方程(R^(2)=0.726);土壤有机质含量、pH值对矮嵩草草甸N_(2)O排放速率的正向直接作用较强,而土壤湿度和容重与高寒草甸N_(2)O排放速率间存在负向直接作用关系。各因素通过影响土壤有机质和铵态氮,对土壤N_(2)O排放均具有较大的间接影响,土壤有机质通过影响高寒草地生物量、土壤硝态氮、铵态氮而间接影响草地生态系统N_(2)O排放速率的作用较强。

Observation data from ocean and terrestrial ecosystems show evidence for the global changes in global natural ecosystems.This study was conducted in Qinghai Haibei Alpine Grassland Ecosystem National Observation and Research Station.The N_(2)O emission characteristics of alpine meadow were monitored by static chamber gas chromatography at the peak growing season of alpine Kobresia humilis meadow.Based on multiple linear regression and path analysis,the effects of soil chemical properties and aboveground biomass on N_(2)O emission from alpine grassland ecosystem were analyzed.The N_(2)O emission rate of alpine meadow showed significant temporal heterogeneity across the growing season,with an average rate of approximate(39.3±5.4)μg/(m^(2)·h).There was significant difference among different months.A better multiple linear regression equation could be established between soil chemical properties,aboveground biomass and N_(2)O emission rate(R^(2)=0.726).There was a positive correlation between the N_(2)O emission rate and soil organic matter,and pH value.However,there was a negative correlation between soil moisture,soil bulk and N_(2)O emission rate of alpine meadow.Other factors indirectly affected N_(2)O emissions by affecting soil organic matter and ammonia nitrogen.Soil organic matter indirectly affected N_(2)O emission rate of grassland ecosystem through aboveground biomass,soil nitrate nitrogen and ammonium nitrogen.In addition,this study showed its great significance for deepening the theory of nitrogen cycle in alpine grassland and exploring the strategies for the mitigation of N_(2)O emission.