长期不同施肥制度对水稻土氨氧化微生物数量和群落结构的影响

Effects of long-term different fertilization regimes on the abundance and community structure of ammonia oxidizers in paddy soils

由氨氧化微生物驱动的氨氧化过程是硝化作用的限速步骤,在土壤氮素循环过程中扮演着重要角色.以湖南省宁乡县长达30 a定位试验水稻土壤为研究对象,采用荧光定量PCR和Illumina Mi Seq高通量测序分析方法,以amoA基因为靶标,研究了4种施肥制度[不施肥(CK)、化肥(CF)、70%化肥+30%有机肥(CFM_1)和40%化肥+60%有机肥(CFM_2)]水稻土壤氨氧化微生物的数量和群落结构变化.结果表明:不同施肥处理氨氧化古菌(AOA)和氨氧化细菌(AOB)amoA基因拷贝数分别为3.09×10~7～8.37×10~7和1.04×10~7～7.03×10~7copies·g^(-1)干土.施肥显著提高了AOA和AOB数量,但处理CFM_2中AOB数量与CK差异不显著.有机肥配施比例对AOB群落α多样性指数的影响强于AOA,处理CFM_1中AOA群落的多样性指数(Shannon)和AOB群落的丰富度指数(ACE和Chao1)均显著高于CK.奇古菌门和泉古菌门是AOA群落的优势门类群,占AOA amoA基因总序列的83.4%;亚硝化螺菌属、environmental_samples_norank、Bacteria_unclassified和Nitrosomonadales_unclassified是AOB群落的优势属类群,占AOB amoA基因总序列的97.8%.维恩分析结果显示,有机肥配施比例对AOB群落操作分类单元(OTU)数量的影响强于AOA,但对各处理共有AOA和AOB amoA基因序列条数的影响均较小.冗余分析结果显示,不同施肥处理AOB群落结构差异强于AOA,且所有土壤理化性质均与AOA和AOB群落结构存在显著相关关系.综上可知:有机肥配施比例显著改变了AOA和AOB数量、多样性和群落结构,配施30%有机肥时,AOA群落的Shannon指数最高,AOB群落数量、ACE和Chao1指数均最高.研究结果可为进一步探讨农业系统中氨氧化微生物对不同施肥制度的响应机制及其在氮素转化中的作用提供科学依据.

Ammonia oxidation,driven by the ammonia oxidizers,is the rate-limiting step of nitrification and plays a key role in soil nitrogen cycling. In this study,real-time PCR and Illumina Mi Seq sequencing approaches were used to investigate the effects of long-term different fertilization regimes on the abundance and community structure of ammonia oxidizers,targeting the amoA genes,in a 30-year located experimental paddy soil in Ningxiang County,Hunan Province. Four treatments were compared,including control without fertilizer（CK）,fertilizers NPK（CF）,70%NPK plus 30% manure（CFM1）,and 40% NPK plus 60% manure（CFM2）. The results showed that the abundance of amoA genes in AOA and AOB was in the range of 3.09×10^7-8.37×10^7 and 1.04×10^7-7.03×10^7 copies·g^（-1） dry soil,respectively. Fertilization significantly increased the AOA and AOB abundances. However,no significant difference was observed in AOB abundance between CFM2 and CK. Manure fertilization rate greatly affected the α diversity index of AOB rather than AOA. The Shannon index of AOA and ACE and Chao1 indexes of AOB observed in CFM1 were significantly higher than that in CK,respectively. Thaumarchaeota and Crenarchaeota were the predominant AOA phyla and Nitrosospira,environmentalsamplesnorank,Bacteriaunclassified and Nitrosomonadalesunclassified were the main AOB genus groups which accounted for 83. 4% and 97.8% of the total AOA and AOB amoA gene reads,respectively. Venn diagram indicated that manure fertilization rate had a stronger effect on the OTU number of AOB amoA gene than that of AOA in different treatments,but it slightly altered the proportion of shared AOA and AOB amoA gene reads. Furthermore,there were pronounced differences in the community structure of AOB among different treatments than that of AOA. These results suggested that manure fertilization rate significantly affected the abundance,diversity and community structure of AOA and AOB. The Shannon index of AOA and the abundance and ACE and Chao1 indexes of AOB in CFM1 were significantly higher than that in the rest treatments,respectively. Our results provided basis for further exploring the response mechanism of ammonia oxidizers to different fertilization strategies and the roles of ammonia oxidizers in nitrogen transformation in agricultural systems.