盐碱土壤N2O排放与amoA和narG功能基因丰度的响应规律

The Response Rule of Functional Gene Abundance of amoA and narG on Nitrous Oxide Emissions in Saline-alkali Soils

为揭示盐碱土壤中参与氨氧化过程和硝酸盐还原过程的amoA和narG基因丰度与N2O排放的响应规律,本研究选取内蒙古河套灌区3种不同盐碱程度土壤(轻度盐土SA、强度盐土SB和盐土SC),通过控制室内温度和土壤质量含水量进行室内培养试验,并运用荧光定量PCR(real-time PCR)技术研究了盐碱土壤中N2O排放速率、氨氧化细菌和narG(膜结合型硝酸还原酶)型反硝化细菌丰度与土壤环境因子之间的偶联关系。结果表明:SA、SB和SC3种盐碱土壤中,N2O平均排放速率随着土壤盐碱程度的升高而升高,值分别为16.9、30.8、69.6μg/(kg·d);氨氧化细菌和narG型反硝化细菌丰度分别为0.415×10^4、6.91×10^4、9.44×10^4 copies和2.61×10^4、5.36×10^4、13.5×10^4 copies,表明在一定盐分条件下,土壤中的盐分能够促进氨氧化细菌和narG型反硝化细菌丰度。RDA分析结果显示,N2O平均排放速率与氨氧化细菌和narG型反硝化细菌丰度具有显著的正相关(r=0.863、0.975,P<0.01);土壤pH、EC、速效钾和有机碳是盐碱土壤中影响N2O排放速率的主要环境因子,其中,土壤pH、EC、速效钾和N2O排放速率存在显著正相关(r=0.968、0.983、0.987,P<0.01),土壤有机碳和N2O排放速率存在负相关(r=–0.800,P<0.05),土壤有效磷和总氮与N2O排放速率的相关性未达到显著水平(P>0.05)。

To reveal the response of N2O emission to the abundances of ammonia-oxidizing bacteria(amoA)and narG(membrane-bound nitrate reductase)genes,a culture experiment was conducted with light saline soil(SA),heavy saline soil(SB)and saline soil(SC)under controlled temperature and moisture to study the effects of soil environmental factors on N2O emission rates and the abundances of amoA and narG genes by real-time PCR.Average N2O emission rates were 16.9,30.8 and 69.6μg/(kg·d)for SA,SB and SC,respectively,significantly increased with the degree of salinization.The abundances of AOB were 0.415×10^4 copies(SA),6.91×10^4 copies(SB)and 9.44×10^4 copies(SC),while the abundances of narG were 2.61×10^4 copies(SA),5.36×10^4 copies(SB)and 13.4×10^4 copies(SC),respectively,indicating that the salinity stimulates the abundances of AOB and narG-type denitrifying bacteria.The RDA analysis showed that the average N2O emission rate positively correlated with the abundances of AOB(r=0.863,P<0.01)and narG(r=0.975,P<0.01).pH,conductivity,available potassium and soil organic carbon are the main environmental factors affecting N2O emission rate,they significantly correlated with N2O emission rate with the coefficients of 0.968,0.983,0.987(P<0.01)and–0.800(P<0.05),respectively.The correlations between N2O emission rate and soil available phosphorus and total nitrogen contents were not significant(P>0.05).