1.Nanjing University of Information Science and Technology;2.State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences
the National Natural Science Foundation of China
【目的】硝化微生物在农田土壤氮转化过程发挥重要作用，深入开展团聚体中硝化微生物分布研究，有助于揭示土壤结构-微生物-土壤营养元素循环间的相互影响机制。【方法】选取旱地黄棕壤为研究对象，比较了玉米连作（M-M）和玉米/花生轮作（M-P）两种种植方式下土壤团聚体的性质和硝化潜势（NP）的变化，并通过荧光定量PCR和高通量测序研究了团聚体中不同类型硝化微生物功能基因的丰度和群落组成差异。【结果】与M-M相比，M-P能够显著提高团聚体pH、NH4+和全碳（TC）含量。M-P使NP显著提高，但团聚体粒径对NP无显著影响。氨氧化细菌（AOB）amoA基因丰度在M-P中高于M-M，且在较小粒级团聚体中分布更多，而氨氧化古菌（AOA）和全程氨氧化细菌（Comammox）amoA基因的分布模式与AOB大致相反，表明AOB更能适应较小团聚体环境，而AOA和Comammox倾向在较大团聚体中占据竞争优势。此外，与M-M相较，M-P团聚体间AOA/AOB和Comammox/AOB比值的差异减小，表明轮作促使土壤硝化微生物在不同粒级间的分布更加均匀。进一步对属水平土壤团聚体硝化菌群落组成分析，结果显示M-P提高了Nitrolancea属亚硝酸盐氧化细菌（NOB）和Candidatus Nitrosocosmicus属AOA的占比，降低了Nitrospira属NOB的占比，对AOB各属无显著影响。而团聚体粒径仅对Nitrosospira属AOB的占比产生显著影响。NH4+含量和pH是影响土壤团聚体NP和硝化微生物群落变化的最主要因子。NP与AOB amoA基因丰度显著正相关，与AOA amoA基因丰度负相关。但在群落组成上，Nitrosospira属AOB，Candidatus Nitrosocosmicus属AOA和Nitrospira属NOB均与NP呈现正相关。【结论】土壤团聚体粒径和种植方式能较大程度影响硝化微生物的分布，然而，不同硝化微生物在团聚体间分异机制具有明显差异，该研究为完善禾豆轮作下土壤硝化微生物在微域环境的生态适应机制提供了理论支持。
Abstract: 【Objective】 Nitrifiers play an important role in the process of farmland soil nitrogen transformation. A study on the distribution of nitrifying microorganisms in aggregates will help to reveal the interaction mechanism between soil structure, microorganisms and soil nutrient cycling. 【Method】The changes in soil aggregate properties and nitrification potential (NP) in maize monoculture (M-M) and maize peanut rotation (M-P) were compared, and the abundance and community composition of different nitrifying functional genes in soil aggregates were evaluated by quantitative PCR and high-throughput sequencing. 【Result】Compared with M-M, M-P significantly increased pH, NH4+ and total carbon (TC) in soil aggregates. M-P also significantly enhanced NP, but the aggregate size had no significant effect on NP. The abundance of the AOB amoA gene was higher in M-P and also more abundant in smaller aggregates. The distribution pattern of AOA and comammox amoA genes was opposite to that of AOB, indicating that AOB can better adapt to the micro-environment of smaller aggregates, while AOA and comammox tended to dominate in larger aggregates. In addition, compared with M-M, the difference in AOA/AOB and comammox/AOB ratio between M-P aggregates decreased, indicating that rotation promoted an even distribution of soil nitrifiers among different aggregate sizes. By further analysis of the nitrifying community based on the 16S rRNA gene sequencing, the results showed M-P increased the proportion of Nitrolancea-like NOB and Candidatus Nitrosocosmicus-like AOA, decreased the proportion of Nitrospira-like NOB, and had no significant effect on AOB compositions. The aggregate size only had a significant effect on the proportion of Nitrosospira-like AOB. NH4+ content and pH were the main factors affecting soil NP and the nitrifying microbial community structure among soil aggregates. NP was positively correlated with AOB amoA gene abundance and negatively correlated with AOA amoA gene abundance. However, in terms of community composition, Nitrosospira-like AOB, Candidatus Nitrosocosmicus-like AOA and Nitrospira-like NOB all showed positive correlations with NP.【Conclusion】Soil aggregate size and cropping system can greatly affect the distribution of nitrifying microorganisms in soil aggregates. However, nitrifying microorganisms have different adaptation mechanisms among aggregates. This study provides a theoretical support for improving the ecological adaptation mechanism of soil nitrifying microorganisms in the micro-environments under Gramineae-Legume rotation.
Xia Weiwei, Li Yikun, Zhang Meng, Sun Xiangxin, Wang Yufang, Jia Zhongjun. Distribution Patterns of Nitrifiers within Soil Aggregates under Different Cropping Systems[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202203220126,[In Press]