为了研究氮沉降对内蒙古贝加尔针茅草原主要温室气体CO_2、CH_4和N_2O通量的影响,试验通过施加NH_4NO_3以模拟氮沉降增加,设置对照(0 kg N·hm~(-2),CK)、低氮(30 kg N·hm~(-2),N30)、中氮(50 kg N·hm~(-2),N50)和高氮(100 kg N·hm~(-2),N100)4个氮素添加水平,于牧草生长季(610月),采用静态箱-气相色谱法测定了CO_2、CH_4和N_2O的通量。结果表明:贝加尔针茅草原是CO_2和N_2O的源、CH_4的汇,与对照相比,氮素添加处理(N30、N50和N100)在显著增加植物地上生物量的同时,增加了CO_2和N_2O的累计排放量,并降低了CH_4的累计吸收量,处理间全球增温潜势表现为N100>N30>N50>CK,所以N50处理既能显著增加草原植物地上生物量,又能够减缓全球增温潜势的增加。相关分析表明:3种温室气体排放通量与土壤温度、有机碳和NO_3~--N含量均显著相关(P< 0.05),CO_2和N_2O排放通量与土壤含水率显著正相关(P<0.05),CH_4和N_2O排放通量与土壤NH_4~+-N含量极显著相关(P<0.01)。
英文摘要:
There is great significance in exploring the response of temperate meadow steppes to global climate change. The dynamics of greenhouse gas(CO_2, CH_4, and N_2O)fluxes are essential for such; thus, the response of a grassland ecosystem to nitrogen addition in a Stipa baicalensis grassland in Inner Mongolia was measured. Four nitrogen addition levels of 0(CK), 30(N30), 50(N50), and 100(N100)kg N· hm~(-2) were used to determine the effects of nitrogen addition on greenhouse gas emissions during the growing season(June to October), using the methods of static chamber-box gas chromatography. We found that the Stipa baicalensis grassland was a source of CO_2 and N_2O, but a sink for CH_4. Nitrogen addition increased the above-ground biomass of the plants significantly and enhanced the emissions of CO_2 and N_2O, whereas it decreased the uptake of CH_4. The global warming potential of the treatments followed the order of N100>N30>N50>CK. Thus, N50 treatment not only significantly increased the above-ground biomass, but also reduced the increase of global warming potential. The fluxes of CO_2, CH_4 and N_2O showed significant correlations with soil temperature, organic carbon and NO_3~- -N content (P<0.05). CO_2 and N_2O fluxes also showed significantly positive correlations with soil moisture(P<0.05). In addition, CH_4 and N_2O fluxes had significant relationships with soil NH_4~+-N content(P<0.01).