放牧牲畜粪尿返还对季节性冻融高寒草原N_(2)O排放的影响

Impacts of Grazing Livestock Dung and Urine Returning on N_(2)O Emission from Seasonal Freeze-thaw Alpine Steppe

放牧牲畜粪尿斑块是草地氧化亚氮(N_(2)O)排放的热点区域,季节性冻融会不同程度改变粪尿养分返还效率和土壤特性,使粪尿作用下的土壤N2O排放特性复杂且作用机理尚不明确。本文采用静态箱-气相色谱法开展为期1年的野外控制试验,探究牦牛和藏绵羊粪尿处理对季节性冻融藏北高寒草原土壤氮动态及N_(2)O排放通量的影响和可能的作用机制。结果表明:尿液施加对土壤N2O排放的短期促进作用明显,且均在处理第1天达到排放通量峰值;牦牛粪尿施加对土壤矿化氮含量的增加更为突出,且牛粪和牛尿处理N_(2)O年累积排放量显著高于羊粪和羊尿处理(P<0.05);冻融期各处理N_(2)O累积排放量占全年的比例为29.3%~42.4%,且消融期对非生长季的贡献最大。研究结论有助于为优化牲畜排泄物管理模式和促进季节性冻融高寒草地温室气体减排等提供理论参考。

Grazing livestock dung and urine patches are hotspots of nitrous oxide(N_(2)O)emissions from grasslands ecosystem.Seasonal freeze-thaw can affect the dung and urine nutrient returning efficiency,alter soil properties,and therefore result in complicated properties and functional mechanism of soil N_(2)O emission.In order to explore the aforementioned issue,this study conducted a one-year field experiment in Xainza Alpine Steppe and Wetland Ecosystem Observation Station of Chinese Academy of Sciences using the method of static box gas chromatography.Field experiment included treatments of yak and Tibetan sheep dung and urine application and was to investigate the soil nitrogen dynamics,N_(2)O fluxes,and possible mechanisms influenced by dung and urine deposition in seasonal freeze-thaw alpine steppe of northern Tibet.The results showed that:(1)Urine application had a stronger short-term stimulating effect on soil N_(2)O emission,with all of urine treatments,showing the highest N_(2)O fluxes on the first day of urine application.(2)Yak dung and urine application significantly increased soil mineral nitrogen concentration,and the cumulative N_(2)O emissions from yak dung and yak urine treatments were significantly higher than those from Tibetan sheep dung and Tibetan sheep urine treatments.(3)Cumulative N_(2)O emissions from each treatment during the freeze-thaw period accounted for 29.3%~42.4%of the total emissions through the whole experimental period,and the thawing period had the greatest contribution to the non-growing season.The conclusions of this study will provide theoretical reference for optimizing the livestock excrement management model and reducing greenhouse gas emission in seasonal freeze-thaw alpine grasslands.