Soil salinity regulation of soil microbial carbon metabolic function in the Yellow River Delta, China

The ecological consequences of soil salinization, one of the major causes of soil degradation worldwide, on soil carbon (C) emissions are well known, but less is known about the related microbial C metabolic function. We conducted laboratory incubation experiments on soil samples under a salt gradient at four levels (non-saline, low, medium, and high salinity soils) from coastal saline-alkaline soil of the Yellow River Delta, China, to assess the role of soil salinity in regulating C emissions and microbial abundance. We also evaluated the associations be-tween salt content and the read number of microbial C metabolism genes by determining the soil metagenomes. We found that soil salinity was negatively related to soil C, nitrogen (N) content, C emissions, bacterial gene copy number, and the relative abundances of Actinobacteria, Thermoleophilia, and Betaproteobacteria, but positively re-lated to the C/N ratio and the relative abundance of Gemaproteobacteria and Halobacteria. Increases in soil salinity correlated with decreases in carbohydrate metabolism and gene abundances of glycosyl transferases and glyco-side hydrolases based on the metagenomic data. In contrast, the enzyme active genes of carbohydrate esterases and auxiliary activities were positively related to soil salinity. This study provides a clear understanding of the re-sponse of soil microbial communities and their C metabolic functions to soil salinity. We offer evidence that soil salinity has significant effects on microbial communities and soil C metabolic functions, resulting in an overall negative effect on soil C emissions. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study revealed that soil salinity significantly influences soil microbial communities and their C metabolic functions, promoting the relative abundance of certain microbial populations while suppressing others, ultimately resulting in a negative impact on soil C emissions.