土壤稳定性有机碳组分与优势细菌门类陆向分布及相关性

Landward distribution and association of the soil stable organic carbon fractions and dominant bacterial phyla

摘要:

【目的】为了探究土壤稳定性有机碳组分和优势细菌门类的陆向分布特征及相关性。【方法】本文选择锡林河流域沿着由水及陆的方向依次采集长期性水流、季节性水流、长期性无水流的湿地及旱地土壤，基于国际腐殖物质协会推荐的方法和16S rRNA基因高通量测序技术分别检测土壤稳定性有机碳组分(富里酸、胡敏酸、胡敏素)含量和优势细菌门类的相对丰度，结合Pearson相关性及冗余分析和结构方程模型研究两者的相关性。【结果】三类稳定性有机碳及酸杆菌门、放线菌门、芽单胞菌门呈大致升高的陆向分布趋势，在长期性无水流的旱地土壤中达到峰值；拟杆菌门则呈现降低的陆向分布趋势。结果显示，芽单胞菌门、酸杆菌门和放线菌门作为长期性无水流旱地土壤的优势细菌门类与胡敏酸、胡敏素含量存在显著(P<0.05)或极显著(P<0.01)正相关关系；拟杆菌门作为长期和季节性水流湿地土壤的优势菌门与富里酸、胡敏酸、胡敏素的含量均呈极显著(P<0.01)负相关关系。结构方程模型结果显示，稳定性有机碳组分与优势细菌门类间存在直接和间接作用。【结论】锡林河流域土壤稳定性有机碳组分及优势细菌门类存在陆向分布特征，稳定性有机碳的升高与芽单胞菌门、酸杆菌门、放线菌门有关，其降低与拟杆菌门的增加有关。

Abstract:

[Objective] To explore the landward distribution and association of the soil stable organic carbon (SOC) fractions and dominant bacterial phyla. [Methods] Along the gradient from the long-term flow with no plant (Np) or Juncellus serotinus (Js), seasonal flow with Juncus effusus (Je) and Potentilla anserina (Pa) to long-term no-flow with Leymus chinensis (Lc) and Stipa grandis (Sg), we collected soil samples in wetland and dryland from Xilin River Basin. We detected the content of SOC fractions [fulvic acid (FA), humic acid (HA), and humin (HM)] in different vegetation zones with the method recommended by International Humic Substances Society (IHSS). Meanwhile, we checked the relative abundance of dominant bacterial phyla by high-throughput sequencing of 16S rRNA gene. Furthermore, we analyzed the association between SOC fractions and dominant bacterial phyla based on Pearson’s correlation analysis, redundancy analysis (RDA), variation partitioning analysis (VPA), and structural equation modeling (SEM). [Results] The SOC fractions (FA, HA, HM), Acidobacteria, Actinobacteria, and Gemmatimonadetes demonstrated the landward distribution with an increasing trend, and peaked in the dryland zone from the long-term no-flow area, whereas Bacteroidetes showed the landward distribution with a decreasing trend. As the dominant bacterial phyla in dryland zone from the long-term no-flow area, Gemmatimonadetes, Acidobacteria, and Actinobacteria showed significantly (P<0.05 or P<0.01) positive correlation with HA and HM. As the dominant bacterial phyla in wetland zone from long-term flow and seasonal flow areas, Bacteroidetes had a significantly (P<0.01) negative correlation with FA, HA, and HM. SEM revealed the direct and indirect links between SOC fractions and dominant bacterial phyla. [Conclusion] SOC fractions and dominant bacterial phyla exhibit obvious landward distribution in Xilin River Basin. The increase of soil SOC fractions is associated with the increase of Gemmatimonadetes, Acidobacteria, and Actinobacteria, and the decrease of Bacteroidetes.