浅层地下水升降对菜地土壤剖面硝化/反硝化微生物丰度的影响

Effects of shallow groundwater fluctuations on the abundances of nitrification and denitrification microbes in the soil profile of vegetable field

为揭示湖泊近岸浅层地下水升降对菜地土壤剖面硝化与反硝化功能微生物基因丰度的影响,以洱海湖滨带菜地土壤剖面为研究对象,通过模拟地下水升降过程,分析了水位升高(S1)、水位降低(S2)及落干(S3)过程中土壤剖面AOA-amoA、AOB-amoA、nirK、nirS、nosZ基因丰度的变化特征,探讨了功能基因与土壤环境因子的耦合关系.结果表明:S3阶段的土壤剖面AOA-amoA和AOB-amoA基因丰度显著高于S1和S2;S1阶段的土壤剖面nirK、nirS、nosZ基因丰度均显著高于S2和S3.AOA-amoA基因丰度显著高于AOB-amoA基因丰度,nirS基因丰度显著高于nirK、nosZ基因丰度;不同取样时期的土壤剖面AOA-amoA、AOB-amoA、nirK、nirS、nosZ基因丰度均表现为A层>B层>C层>D层.水位升降对土壤剖面AOA-amoA、AOB-amoA、nirK、nirS、nosZ基因丰度有显著影响,且AOA-amoA和nirS基因对水位升降更敏感,分别在硝化与反硝化作用中占主导地位;pH、有机碳(SOC)、全氮(TN)为功能基因AOA-amoA、AOB-amoA的环境驱动因子,而功能基因nirK、nirS、nosZ的环境驱动因子为土壤含水量(W)、铵态氮(NH4^+-N)、硝态氮(NO3^--N)、TN、SOC、pH.该研究结果可为揭示浅层地下水升降过程中菜地土壤剖面氮素循环的微生物学机制提供科学依据.

In order to reveal the effects of shallow groundwater fluctuations on the abundances of functional genes associated with nitrification and denitrification microbes in soil,vegetable field soil in the lakeside area of the Erhai Lake was taken as the research object,and the variation of abundances of AOA-amoA,AOB-amoA,nirK,nirS and nosZ in soil profiles ware analyzed during rising(S1),falling(S2)of water level and drying(S3)by simulating the groundwater table.The coupling relationships between functional genes and soil environmental factors were discussed.The results show that the abundances of AOA-amoA and AOB-amoA in soil profiles in the stage S3 were significantly higher than that in the stages S1 and S2.The abundances of nirK,nirS and nosZ in the soil profile in the stage S1 were significantly higher than those in the stages S2 and S3.The gene abundance of AOA-amoA was significantly higher than that of AOB-amoA.The gene abundance of nirS was significantly higher than that of nirK and nosZ.The abundances of AOA-amoA,AOB-amoA,nirK,nirS and nosZ in different soil layers in different sampling periods were as follows:A layer>B layer>C layer>D layer.The rising and falling of water table had significant effects on the gene abundances of AOA-amoA,AOB-amoA,nirK,nirS and nosZ in soil profile.The AOA-amoA and nirS weredominant genes in the nitrification and denitrification,respectively,and were more sensitive to the fluctuation of water level.pH,organic carbon(SOC)and total nitrogen(TN)were the main environmental driving factors of the AOA-amoA and AOB-amoA,and the main environmental driving factors of the nirK,nirS and nosZ are soil moisture content(W),ammonium nitrogen(NH+4-N),nitrate nitrogen(NO-3-N),TN,SOC,pH.The results of this study provide a scientific basis for revealing the microbial mechanism of nitrogen cycling process in the soil profile of vegetable fields under the groundwater table fluctuations.