水位波动和氮浓度变化对氮转化功能基因丰度的影响

Effects of water table fluctuations and nitrogen concentration variations on the abundances of nitrogen-transforming functional genes in soil profiles

为探索浅层地下水氮浓度及水位波动对土壤剖面中氮转化功能基因丰度的影响,以洱海近岸农田原状土壤剖面为对象,研究了模拟常规氮浓度的浅层地下水进行水位波动(SND)和持续淹水(SNF),以及无氮浓度的浅层地下水位波动(0ND)后土壤剖面氮浓度和氮转化功能基因丰度的变化,探讨了土壤因子与功能基因丰度的关系.结果表明:SNF、SND和0ND处理较试验前土壤剖面中溶解性总氮(TDN)浓度分别降低了44%、21%和30%,NO_(3)^(−)-N浓度分别降低了55%、28%和38%.同时,0ND和SNF处理较SND处理土壤剖面中反硝化功能基因丰度分别降低20%和1%,厌氧氨氧化功能基因丰度则分别增加68%和7%,硝化功能基因丰度分别降低34%和增加23%,土壤含水率(MC)、NH_(4)^(+)-N、NO_(3)^(−)-N和TDN均为功能基因丰度变化的重要驱动因子.土壤剖面持续淹水会显著降低溶解性氮浓度,浅层地下水波动及水中氮浓度引起的土壤剖面干湿交替和氮浓度变化是氮转化功能基因丰度变化的主要驱动力.

To explore the effects of nitrogen concentration in shallow groundwater and its water table fluctuations on the abundance of soil nitrogen-transforming functional genes,taking the undisturbed soil profile from cropland around Erhai as the object,changes in nitrogen concentrations and abundance of nitrogen-transforming functional genes in soil profiles under shallow groundwater table fluctuations(SND)and continuous flooding(SNF)with conventional nitrogen concentration,and shallow groundwater table fluctuations(0ND)without nitrogen were studied.The relationship between soil environmental factors and abundance of functional genes was discussed.The results indicated that,compared with the nitrogen concentrations in soil profile before the microcosmic experiment,the total dissolved nitrogen(TDN)concentrations in SNF,SND and 0ND decreased by 44%,21%and 30%,and NO_(3)^(−)-N concentrations decreased by 55%,28%and 38%,respectively.Meanwhile,compared with the abundance of nitrogen-transforming functional genes in soil profile in SND,the denitrification function gene abundances in 0ND and SNF decreased by 20%and 1%,while the anammox function gene abundances increased by 68%and 7%,and the nitrification function gene abundances decreased by 34%and increased by 23%,respectively.Changes in functional gene abundances were mainly driven by soil moisture content(MC),NH_(4)^(+)-N,NO_(3)^(−)-N and TDN.In conclusion,continuous flooding in soil profiles would significantly reduce dissolved nitrogen concentrations,and changes in alternation of drying-flooding and nitrogen concentrations in soil profile caused by the nitrogen concentrations in shallow groundwater and its water table fluctuations were the main drivers for changes in the abundance of nitrogen-transforming functional genes.