红黄泥水稻土剖面细菌群落构建及功能特征

Assembly and functional characterization of the bacterial community of reddish clayey paddy soil profile

摘要:

【背景】细菌群落在水稻土剖面的垂直分布对稻田土壤的形成和养分循环等有着重要影响，而剖面发生层细菌群落构建和功能特征尚不清楚。【目的】探究水稻土剖面各发生层细菌群落特征和功能差异，以及发生层细菌群落结构的驱动机制。【方法】选择第四纪红色黏土发育的红黄泥水稻田作为研究对象，挖掘剖面，依据剖面诊断层次划分土壤发生层，采集各发生层土壤样品，最后通过高通量测序技术进行分析。【结果】耕作层(Ap1, 0−19 cm)细菌群落的α多样性显著高于其他发生层，β分析表明垂直方向上剖面细菌群落结构存在显著差异。绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteriota)等相对丰度随土壤发生层深度的增加而减少，而GAL15和脱硫弧菌门(Desulphurvibrio)等则相反；甲基菌门(Methylomirabilota)、硝化螺旋菌门(Nitrospirota)等随土壤发生层深度的增加呈现先增加再减少，变形菌门(Proteobacteria)等随土层深度的增加呈现先减少再增加。土壤有效磷(available phosphorus)和土壤有机质(soil organic matter, SOM)显著促进了土壤剖面的细菌多样性，有机质、总钾(total potassium)、硝态氮(nitric nitrogen)是影响细菌群落构建的主要环境因子。TaxFun2分析表明，细菌群落功能在剖面发生层之间存在显著性差异，在Ap1 (0−19 cm)、Ap2 (20−30 cm)、BrC (95−112 cm)的功能较为强烈，在水耕氧化还原层Br (31−94 cm)较弱。表层土壤和接近母质层的土壤中拥有更多的独特细菌类群。高丰度和低丰度的细菌类群都对细菌网络的连通性起到重要作用。确定性过程主导了剖面细菌群落的构建。【结论】红黄泥水稻土剖面细菌群落结构和功能存在显著差异，确定性过程主导了剖面细菌群落的构建。

Abstract:

[Background] The vertical distribution of bacterial communities impacts the formation and nutrient cycling of paddy soils, while the assembly and functional characteristics of bacterial communities in different soil genetic horizons remain unclear. [Objective] To explore the characteristics and functional differences of bacterial communities in different paddy soil genetic horizons and reveal the driving mechanism of bacterial community assembly in each horizon. [Methods] The reddish clayey paddy soil was excavated and profiled, and soil samples were collected from different soil genetic horizons. The bacteria in each horizon were analyzed by high-throughput sequencing. [Results] The α diversity of the bacterial community in the cultivated horizon (Ap1, 0−19 cm) was significantly higher than that in the other horizons. The β diversity analysis showed that the bacterial community structure was significantly different among different horizons. The relative abundance of Chloroflexi and Acidobacteriota decreased with the increase in soil depth, while that of GAL15 and Desulphurvibrio showed the opposite trend. As the soil horizon deepened, the relative abundance of Methylomirabilota and Nitrospirota first increased and then decreased, while that of Proteobacteria first decreased and then increased. Available phosphorus and soil organic matter significantly improved bacterial diversity in the soil, and soil organic matter, total potassium, and nitric nitrogen were the main environmental factors affecting the bacterial community assembly. The TaxFun2 analysis showed that there were significant differences in bacterial community functions among different soil horizons, with stronger metabolism in Ap1 (0−19 cm), Ap2 (20−30 cm), and BrC (95−112 cm) horizons and weaker metabolism in the Br horizon (31−94 cm). Surface soil and the soil close to the parent material had more unique bacterial taxa than other soil horizons. Both the bacteria taxa with high relative abundance and those with low relative abundance played a role in the bacterial network connectivity, and deterministic processes dominated the bacterial community assembly of the soil profile. [Conclusion] There are significant differences in the structure and function of bacterial communities of the reddish clayey paddy soil profile, and deterministic processes dominate the bacterial community assembly.