锡林河流域不同植被带土壤绿菌门微生物群落的空间分布特征

目的] 为了探究锡林河流域中游不同植被带土壤绿菌门（Chlorobi）成员的空间分布特征及驱动因子。方法] 本文选择典型河滨带环境为研究对象，沿河流中心至河流阶地（陆向）方向，在无植被带（BC）、水莎草沼泽（BS）、灯芯草沼泽化草甸（LF）、鹅绒委陵菜草甸（HF）、河流阶地羊草草原（LT）、丘陵坡地大针茅典型草原（HT）中分别采集0-10 cm土壤样品。基于16S rRNA基因高通量测序分析土壤绿菌门微生物群落的组成、丰度及空间分布特征；结合土壤理化因子分析绿菌门微生物群落空间异质性的驱动因子。结果] 在属水平上共检测到来自绿菌目（Chlorobiales）和Ignavibacteriales目的9个类群。Chlorobiales1、2、6及Ignavibacteriales7、9类群的最高相对丰度低于0.40%；Ignavibacteriales3、4、5、8类群的最高相对丰度介于0.54%-1.06%。Chlorobiales1、2类群在HF、LT和HT的相对丰度显著高于BS（P<0.05），Chlorobiales1类群的相对丰度与pH和总有机碳含量呈极显著正相关（P<0.01）；Chlorobiales2类群的相对丰度与粉黏粒含量呈极显著正相关（P<0.01）；Ignavibacteriales3、5、7、9和Ignavibacterium4类群在LF的相对丰度显著高于BC（P<0.05），与含水量呈极显著正相关（P<0.01）；Chlorobiales6和Ignavibacteriales8类群在BS的相对丰度显著高于其他植被带（P<0.05），与氨态氮含量呈极显著正相关（P<0.01）。变异权重分析表明，土壤含水量解释了绿菌门微生物群落空间变异的65.7%。结论] 锡林河流域不同植被带土壤绿菌门微生物群落存在明显的空间异质性；土壤含水量是不同植被带绿菌门微生物群落空间异质性的主要驱动因子。

Spatial distribution characteristics of soil microbial communities from Chlorobi phylum in different vegetation zones from Xilin River Basin

Objective] In this study, the main goal was to explore the spatial heterogeneity and driving factors of soil microbial populations from Chlorobi phylum in different vegetation zones from the middle reach of Xilin River Basin. Methods] We selected the typical riparian vegetation zones along the landward direction from the riverbed center (BC) without vegetation zone to the river terrace. These vegetation zones included Juncellus serotinus-dominated marsh plant communities from riverbed side (BS), Juncus effusus-dominated marsh meadow plant communities from low floodplain (LF), Potentilla anserina-dominated meadow plant communities from high floodplain (HF), Leymus chinensis grassland on the river terrace (LT) and Stipa grandis grassland on a slope in the hilly zone (HT). Meanwhile, we collected 0-10 cm soil samples and analyzed the spatial distribution characteristics, abundance and composition of soil Chlorobi communities based on 16S rRNA gene high-throughput sequencing. To explore the environmental factors driving the spatial heterogeneity of soil microbial communities from Chlorobi phylum, we detected the soil physiochemical factors.Results] Nine populations from the orders Chlorobiales and Ignavibacteriales were detected at genus level. The highest relative abundance of Chlorobiales1, Chlorobiales2, Chlorobiales6, Ignavibacteriales7 and Ignavibacteriales9 were less than 0.40%, while those of the other four populations from order Ignavibacteriales ranged from 0.54% to 1.06%. The relative abundances of both Chlorobiales1 and Chlorobiales2 in HF, LT and HT were higher than those in BS (P<0.05). The abundance of Chlorobiales1 was significantly positively correlated with pH and total organic carbon content (P<0.01), while that of Chlorobiales2 was significantly positively correlated with the content of clay and silt particles (P<0.01). The relative abundances of Chlorobiales6 and Ignavibacteriales8 in BS were higher than those of the other vegetation zones (P<0.05). Their abundances were significantly positively correlated with ammonia nitrogen content (P<0.01). Variation partitioning analysis (VPA) showed that soil water content accounted for 65.7% of the spatial variation of microbial communities from Chlorobi phylum. Conclusion] In the Xilin River Basin, the populations of Chlorobi communities from different vegetation zones demonstrated obvious spatial heterogeneity. Water content was the main driving factor of the spatial heterogeneity of the soil microbial communities from Chlorobi phylum in different vegetation zones.