College of Life and Health Sciences, Northeastern University, 3 Wenhua Road, Shenyang, 110169, People's Republic of China.
Microb Ecol. 2021 Oct;82(3):722-735. doi: 10.1007/s00248-021-01695-x. Epub 2021 Jan 29.
Secondary salinization is a serious environmental issue and a major threat to the sustainable use of grasslands. Information about the response of microbial communities and soil properties in already saline soils to increasing salinity is lacking. We investigated soil properties and the structures of soil bacterial and fungal communities across a gradient of salinization in the Horqin Grassland, China. Three sites with relatively lightly (average soluble salt content = 0.11%), relatively moderately (average soluble salt content = 0.44%), and heavily (average soluble salt content = 1.07%) degraded grassland, were selected as experimental sites. We examined variations in the composition and structure of the soil bacterial and fungal communities by using high-throughput sequencing of the 16S and 18S rRNA genes, respectively. We found degrading effects of salinization on soil properties, i.e., decreased soil moisture, organic matter, total N, NH-N, and NO-N and increased soil bulk density, pH, and electrical conductivity. The bacterial and fungal community structures changed with increasing salinity. However, dominant microbial taxa (including phylum, genus, and operational taxonomic unit levels) were similar among experimental sites, indicating that increasing salinization slightly affected the basic compositions of microbial communities in already saline grasslands. Furthermore, the relative abundances of most dominant taxa sensitively responded to the soil salt content. Acidobacteria, Actinobacteria, Chloroflexi, RB4, Rubrobacter, Blastocatella, H16, Glomeromycota, and Aspergillus linearly increased with increasing salinization, suggesting that they could be used as bioindicators for salt-tolerant communities. Overall, the changes in the structures of soil bacterial and fungal communities were determined by the relative quantities of dominant taxa rather than community composition. The structures of soil bacterial and fungal communities were linked to soil properties and vegetation. Increasing soil salt content, and thereby varied pH and organic matter, were likely the direct influencing factors of microbial communities in these saline grasslands.
次生盐渍化是一个严重的环境问题，也是草地可持续利用的主要威胁。关于已经盐渍化土壤中微生物群落和土壤性质对盐度增加的响应的信息还很缺乏。我们在中国的科尔沁草原的盐渍化梯度上调查了土壤性质和土壤细菌和真菌群落的结构。选择了三个相对轻度（平均可溶性盐含量=0.11%）、中度（平均可溶性盐含量=0.44%）和重度（平均可溶性盐含量=1.07%）退化草地的地点作为实验点。我们分别通过高通量测序 16S 和 18S rRNA 基因来研究土壤细菌和真菌群落的组成和结构变化。我们发现盐渍化对土壤性质有降解作用，即土壤水分、有机质、总氮、NH-N 和 NO-N 减少，土壤容重、pH 和电导率增加。细菌和真菌群落结构随盐度增加而变化。然而，实验点之间主要微生物类群（包括门、属和操作分类单元水平）相似，这表明增加的盐度对已经盐渍化草地中微生物群落的基本组成影响不大。此外，大多数优势类群的相对丰度对土壤盐分含量敏感。酸杆菌门、放线菌门、绿弯菌门、RB4、Rubrobacter、Blastocatella、H16、Glomeromycota 和曲霉门随着盐度的增加呈线性增加，表明它们可以作为耐盐群落的生物标志物。总的来说，土壤细菌和真菌群落结构的变化是由优势类群的相对数量决定的，而不是群落组成。土壤细菌和真菌群落的结构与土壤性质和植被有关。土壤盐分含量的增加，从而导致 pH 和有机质的变化，可能是这些盐渍草地中微生物群落的直接影响因素。
