施氮肥对华北平原土壤氨氧化细菌和古菌数量及群落结构的影响

摘要

利用荧光定量PCR、末端限制性片段长度多样性(T-RFLP)和基因克隆文库技术,比较了4种施氮水平(不施氮肥,0 kgN/hm2,CK;施低水平氮肥,75 kg N/hm2,N1;施中水平氮肥,150 kg N/hm2,N2;施高水平氮肥,225 kg N/hm2,N3)下华北平原地区小麦季表层(0-20 cm)土壤总细菌、氨氧化细菌(AOB)和氨氧化古菌(AOA)的丰度和群落结构.结果表明,土壤总细菌、AOB和AOA数量分别在每克干土5.74× 109-7.50× 109、8.89× 106-2.66× 107和3.83× 108-7.78× 108之间.不同施氮量土壤AOA数量均高于AOB数量,AOA/AOB值在81.72-14.38之间.增施氮肥显著显著提高AOB数量(P＜0.05),对总细菌和AOA数量的影响不显著(P＞0.05).与CK相比,赴理N1、N2和N3中AOB数量分别提高了0.64、1.50和1.99倍.增施氮肥显著改变了AOB和AOA的群落结构,且不同施氮量处理中AOB群落结构差异更大.系统进化分析显示,施氮肥小麦土壤AOB主要为Nitrosospira属类群,分布在Cluster 3的两个分支中;AOA分布在Cluster S的4个分支中.相关性分析显示,AOB数量与全氮和铵态氮含量呈显著正相关关系,与土壤pH和碳氮比呈显著负相关关系(P＜0.05);AOA数量与硝态氮含量和土壤pH呈显著正相关关系,与铵态氮含量呈显著负相关关系(P＜0.05).研究结果表明:增施氮肥可显著改变华北平原地区碱性土壤AOB数量与群落结构,该地区小麦土壤中AOB比AOA对氮肥响应更敏感.%The abundance and community structure of total bacteria ammonia oxidizing bacteria,and archaea were investigated by real-time PCR,T-RFLP,and cloning library approaches in a wheat field under different N fertilization rates (no N fertilization,0 kg N/hm2,CK;low N fertilization rate,75 kg N/hm2,N1;moderate N fertilization rate,150 kg N/hm2,N2;high N fertilization rate,225 kg N/hm2,N3) in North China.The population sizes of total bacteria,AOB and AOA were 5.74× 109-7.50× 109,8.89× 106-2.66× 107 and 3.83× 108-7.78× 108 copies/g dry soil,respectively.The population numbers of AOA were higher than that of AOB in all treatments,with AOA to AOB ratios ranged from 81.72 to 14.38.Significant higher numbers for AOB were detected for the high level of N fertilization soil (P＜0.05),but not in the population of total bacteria and AOA.The population numbers of AOB observed in N1,N2 and N3 were 1.64,2.50 and 2.99 times greater than that in the CK treatment,respectively.The N fertilization rates significantly changed the communities of both AOB and AOA,and more variation was observed in the community of AOB.Phylogenetic results showed that the majority AOB sequences fell into two branches of Cluster 3,affiliated with Nitrosospira species,and all AOA sequences fell within four branches in Cluster S.Significant positive correlations were observed among the population sizes of AOB to total nitrogen and ammonium,and the population sizes of AOA to soil pH and nitrate (P＜0.05).Significantnegative correlations were observed among the population sizes of AOB to soil pH and C/N ratio,and the population sizes of AOA to ammonium (P＜0.05).These results demonstrated that AOB were more sensitive than AOA to N fertilization in alkaline wheat fields in North China.