模拟酸雨对大豆田土壤N2O通量及植株和土壤氮含量的影响

摘要

氧化亚氮(N2O)是一种重要的温室气体,而农田生态系统是N2O的重要排放源.酸雨是中国重要的环境问题,然而少有研究关注酸雨对农田土壤N2O排放的影响.在大豆(Glycine max(Linn.)Merr.)生长季开展了2年的田间模拟酸雨试验,设置了pH值分别为6.7(对照,CK)、4.0(T1)、3.0(T2)和2.0(T3)的4个不同酸雨处理水平,采用静态箱-气相色谱法测定N2O排放通量,以研究模拟酸雨对大豆田土壤N2O排放通量及植株与土壤氮含量的影响.结果表明:与CK相比,酸雨没有改变土壤N2O排放的季节性规律,虽然整个大豆生长季土壤N2O平均通量并没有显著变化,但在第二年大豆鼓粒期,与CK相比,T1和T3处理使土壤N2O平均排放通量分别显著增加35.1%(P=0.020)和71.2%(P=0.000).通过植株和土壤理化分析发现,酸雨处理显著降低了开花—结荚期大豆植株地下生物量,T1和T3处理的地下生物量分别下降了31.93%(P=0.039)和24.30%(P=0.027).在分枝期、开花—结荚期和鼓粒期,各酸雨处理不同程度地降低了叶片可溶性蛋白质含量;在开花—结荚期,酸雨各处理均降低了叶片全氮和硝态氮含量.酸雨处理没有显著改变土壤有机碳及全氮含量,但在分枝期和开花—结荚期,酸雨处理显著减少了土壤硝态氮含量.%Nitrous oxide (N2O) is a typical greenhouse gases and agroecosystem is a significant source of N2O emission. Acid rain is an important environmental issue in China, but few studies have focused on its impact on soil N2O emission in agricultural ecosystem. To investigate the effects of acid rain on soil N2O emission fluxes and the nitrogen content of plant and soil.,field experiments with simulated acid rain were conducted in the soybean (Glycine max(Linn.) Merr.) farmland for two growing seasons. Four experimental treatments were set up, including the control (CK, pH=6.7), pH=4.0 (T1), pH=3.0 (T2), and pH=2.0 (T3). The N2O emission fluxes were measured by the static chamber-gas chromatography method. Results showed that simulated acid rain did not change the seasonal variation pattern of N2O emission fluxes from soil. Although no significant impact of simulated acid rain on the average flux of N2O was observed during the whole soybean-growing season, the average N2O flux under T1 and T3 treatments during grain-filling period of the second year was increased by 35.1% (P=0.020) and 71.2% (P=0.000) than CK, respectively. Compared with CK, T1 and T3 treatments significantly reduced the root biomass by 31.93% (P=0.039) and 24.30% (P=0.02) in the flowering-podding stage. Acid rain treatments reduced the soluble protein content of leaves in the branching, flowering-podding, and grain-filling stages, and decreased the contents of total nitrogen and nitrate nitrogen in leaves during the flowering-podding stage. Acid rain treatments did not significantly change the contents of organic carbon and total nitrogen in soil, while, it significantly reduced the nitrate nitrogen content of soil in the branching and flowering-podding stages.