Soil microorganisms play an indispensable role in the material and energy cycle of grassland ecosystems. The abundance of these organisms vary according to environmental factors, such as time of year and soil depth. There have been few studies on the transformation of soil microbial communities in degraded typical steppe according to these temporal and spatial changes. In this study, we analyze the community structure and diversity of soil bacteria and fungi, and the impact of these changing temporal and spatial factors upon the community structure. From May to September 2018, we collected 90 soil samples from different depths (10, 20, and 30 cm) from the typical degraded steppe area of Xilingol. We carried out studies on soil physical and chemical properties and soil microbial diversity using high-throughput sequencing technology. We found that depth significantly affected abundance and diversity of bacteria and fungi. Bacteria and fungi diversity at 10 cm was higher than that at 20 cm and 30 cm. The abundance of Acidobacteria, Proteobacteria, Actinomycetes, Ascomycetes, and Basidiomycetes varies significantly with depth. In addition, soil pH increased significantly with increasing depth, while soil organic matter (SOM), available nitrogen (AN), volume water content of soil (VWC), and soil temperature (ST) decreased significantly with increasing depth. Finally, the depth, total organic carbon (TOC), and AN had a significant impact on the bacterial and fungal communities’ abundance (p < 0.05). Spatial heterogeneity (in soil depth) is more significant than the time of year (month) in predicting changes in microbial community composition and soil properties. SOM, VWC, and the abundance of Proteobacteria and Actinomycetes positively correlate with soil depth, while pH and the abundance of Acidobacteria, Ascomycetes, and Basidiomycetes negatively correlate with soil depth. We speculate that SOM and VWC account for the variations in the abundance of Acidobacteria and Proteobacteria, while pH causes variations in the abundance of Actinomycetes, Ascomycetes and Basidiomycota.

中文翻译：

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欧亚草原土壤微生物群落随时间和深度的变化

土壤微生物在草原生态系统的物质和能量循环中起着不可或缺的作用。这些生物的丰度根据环境因素而变化，例如一年中的时间和土壤深度。根据这些时空变化，关于退化典型草原土壤微生物群落转化的研究很少。在这项研究中，我们分析了土壤细菌和真菌的群落结构和多样性，以及这些时空变化对群落结构的影响。从2018年5月至2018年9月，我们从锡林郭勒典型退化草原地区收集了90个不同深度（10、20和30厘米）的土壤样品。我们使用高通量测序技术进行了土壤理化性质和微生物多样性的研究。我们发现深度显着影响细菌和真菌的丰度和多样性。10 cm处的细菌和真菌多样性高于20 cm和30 cm处的细菌和真菌多样性。酸性细菌，变形细菌，放线菌，子囊菌和担子菌的丰度随深度的变化而显着不同。此外，土壤pH值随深度增加而显着增加，而土壤有机质（SOM），有效氮（AN），土壤体积含水量（VWC）和土壤温度（ST）随深度增加而显着下降。最后，深度，总有机碳（TOC）和AN对细菌和真菌群落的丰度有显着影响（p <0.05）。在预测微生物群落组成和土壤特性的变化方面，空间异质性（在土壤深度上）比一年中的时间（一个月）更重要。SOM，VWC，蛋白酶和放线菌的丰度与土壤深度呈正相关，而pH和酸菌，子囊菌和担子菌的丰度与土壤深度呈负相关。我们推测，SOM和VWC解释了酸性细菌和变形细菌的丰度变化，而pH值引起了放线菌，子囊菌和担子菌丰度的变化。