Abstract:

To investigate the dynamic changes of nitrogen mineralization of tobacco-planting soil in central Henan and explore the response characteristics of soil microbial diversity and nitrogen cycle function genes to soil moisture condition， the tobacco-planting soil from Xuchang were cultured under 50% （H-50%）， 65% （H-65%）， 80% （H-80%） water conditions to analyze the difference of functional diversity of bacterial and fungal communities. The results showed that the mineralization amount and mineralization rate of soil inorganic nitrogen in H-65% treatment were higher than those in other treatments. Proteobacteria， Actinobacteria， Chloroflexi， Firmicutes， Acidobacteria， Planctomycotes， and Germatimonades were the dominant bacteria at phylum level （relative abundance >3%）. The relative abundance of Proteus in H-80% treatment was significantly higher than other treatments， while the relative abundance of Firmicutes was vice versa. The relative abundances of Actinomyces and Curvularia in H-50% treatment were significantly higher than those in other treatments. Ascomycota accounted for more than 90% of the fungal OTUs（operational taxonmic units）， and its relative abundance showed an inverted “V” trend with the increasing of soil moisture content. The results of LEfSe （LDA effect size） analysis for bacterial showed that 6 active biomarkers （LDA value >3.5） were detected at the genus level. The bacterial community showed abundant functional diversity， the primary functional layer was more active in metabolism， and the functional gene abundance of the secondary functional layer changed obviously under different water content conditions. The relative abundances of nifK， nifD， nifH genes involved nitrogen fixation process showed H-50%>H-65%>H-80%， and the relative abundances of norB， nirK， nosZ genes involved denitrification process were the highest in H-65% treatment. Collectively， the reasonable regulation of soil moisture content might effectively regulate the dynamic change of soil nitrogen mineralization， the functional diversity of soil microbial community and the change of functional genes relating to nitrogen cycle in central Henan tobacco growing areas.

Key words: nitrogen mineralization, soil moisture content, nitrogen cycling, functional genes, soil microbial community structure

摘要：

为揭示豫中典型浓香型烤烟产区植烟土壤氮素矿化动态变化、土壤微生物多样性以及氮素循环功能基因对水分条件的响应特征，通过室内培养法研究50%（H-50%）、65%（H-65%）和80%（H-80%））持水量条件下，河南许昌植烟土壤细菌和真菌群落功能多样性的差异。结果表明，H-65%处理土壤的无机氮矿化量及矿化速率均高于其他处理。在土壤细菌中，变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、绿弯菌门（Chloroflexi）、厚壁菌门（Firmicutes）、酸杆菌门（Acidobacteria）、浮霉菌门（Planctomycetes）、芽单胞菌门（Gemmatimonadetes）为优势菌门（相对丰度>3%），其中，H-80%处理中变形菌门的相对丰度显著高于其他处理，而厚壁菌门的相对丰度显著低于其他处理；H-50%处理中放线菌门、绿弯菌门的相对丰度显著高于其他处理。在土壤真菌中，子囊菌门（Ascomycota）占土壤真菌总OTU（operational taxonmic units）数的90%以上，其相对丰度随土壤含水率增加呈倒“V”的变化趋势。LEfSe（LDA effect size）分析结果表明，各处理在细菌属水平共检测出6种活性生物标志物（LDA值>3.5）。细菌群落具有丰富的功能多样性，一级功能层表现为代谢方面较活跃，二级功能层的功能基因丰度在不同含水率条件下发生明显变化；与固氮过程相关的固氮酶基因nifK、nifD、nifH的相对丰度在不同处理中表现为H-50%>H-65%>H-80%，反硝化过程相关基因norB、nirK、nosZ的相对丰度均在H-65%处理最高。综合来看，合理调控土壤含水率可以有效调节豫中烟区土壤氮素矿化动态、土壤微生物群落功能多样性以及氮循环相关功能基因的丰度。

关键词: 氮素矿化, 土壤含水率, 氮素循环, 功能基因, 土壤微生物群落结构