若尔盖沙化土地治理土壤微生物群落与功能基因比较研究

Comparison of soil microbial communities and functional genes in sandy land management of Zoige

摘要:

【目的】在高寒沙地中建立以赖草和沙生苔草等先锋植物为主的人工草方格，探究其土壤微生物群落动态变化以及养分循环过程。【方法】采用宏基因组测序和qPCR方法进行土壤微生物群落结构组成分析、功能基因注释和绝对丰度测定，并结合土壤理化因子数据进行冗余分析。【结果】人工建立草方格后，沙地土壤中全氮、速效磷以及有机碳含量分别提高了20%-68%、10%-247%、19%-56%；细菌和真菌的群落数量分别提高了17%-81%和2%-95%，与植物促生长相关的鞘氨醇单胞菌属(Sphingomonas)、慢生根瘤菌属(Bradyrhizobium)、硝化螺旋菌属(Nitrospira)、Solirubrobacter属和类诺卡氏菌属(Nocardioides)等细菌种类的相对丰度呈上升趋势；氮循环中与氨氧化和亚硝酸盐氧化相关的amoCAB基因簇和nxrAB基因簇显著富集，发现了完全氨氧化的基因标志。【结论】人工建立草方格有效提升了高寒沙地土壤养分和微生物群落数量，促进了养分循环。适度放牧可以增加沙地生态系统的氮汇扩散性，有助于本土先锋植物定植，为今后在同等高海拔地区采取沙地生态修复措施提供理论参考。

Abstract:

[Objective] To reveal the dynamic changes of soil microbial community and nutrient cycling process in the artificial grass squares dominated by pioneering plants such as Leymus secalinus and Carex praeclara in the alpine sandy land. [Methods] Metagenomic sequencing and qPCR were performed for the structure analysis, functional gene annotation, and absolute abundance determination of soil microbial communities, which were combined with soil physico-chemical factors for redundancy analysis. [Results] The artificial establishment of grass squares increased the total nitrogen by 20%–68%, available phosphorus by 10%–247%, and organic carbon by 19%–56% in sandy soils. Furthermore, it increased the bacterial and fungal abundance by 17%–81% and 2%–95%, respectively. Specifically, it increased the relative abundance of plant growth-promoting bacteria, such as Sphingomonas, Bradyrhizobium, Nitrospira, Solirubrobacter, and Nocardioides. Furthermore, the artificial establishment of grass squares enriched the amoCAB gene cluster and the nxrAB gene cluster associated with ammonia oxidation and nitrite oxidation in the nitrogen cycle. In addition, a genetic signature for complete ammonia oxidation was identified. [Conclusion] The artificial establishment of grass squares increases the content of soil nutrients and microbial abundance and promotes the nutrient cycling in alpine sandy areas. Moderate grazing can increase the diffusivity of nitrogen sinks and promote the colonization of native pioneer plants in the sandy ecosystem. The findings provide theoretical references for future restoration of sandy ecosystems in similar high-altitude areas.