Soil bacterial communities associated with multi-nutrient cycling under long-term warming in the alpine meadow

Abstract

Introduction: The functions of terrestrial ecosystems are mainly maintained by bacteria, as a key component of microorganisms, which actively participate in the nutrient cycling of ecosystems. Currently, there are few studies have been carried out on the bacteria contributing to the soil multi-nutrient cycling in responding to climate warming, which hampers our obtainment of a comprehensive understanding of the ecological function of ecosystems as a whole.

Methods: In this study, the main bacteria taxa contributing to the soil multi-nutrient cycling under the long-term warming in an alpine meadow was determined based onphysichemical properties measurement and high-throughput sequencing, and the potential reasons that warming altered the main bacteria contributing to the soil multi-nutrient cycling were further analyzed.

Results: The results confirmed that the bacterial β-diversity was crucial to the soil multi-nutrient cycling. Furthermore, Gemmatimonadetes, Actinobacteria, and Proteobacteria were the main contributors to the soil multi-nutrient cycling, and played pivotal roles as keystone nodes and biomarkers throughout the entire soil profile. This suggested that warming altered and shifted the main bacteria contributing to the soil multi-nutrient cycling toward keystone taxa.

Discussion: Meanwhile, their relative abundance was higher, which could make them have the advantage of seizing resources in the face of environmental pressures. In summary, the results demonstrated the crucial role of keystone bacteria in the multi-nutrient cycling under the climate warming in the alpine meadow. This has important implications for understanding and exploring the multi-nutrient cycling of alpine ecosystems under the global climate warming.

Keywords: bacteria; climate warming; keystones; multi-nutrient cycling; profile.

Figure 1

The bacterial diversity throughout the entire soil profile under control and warming. The α-diversity of bacteria between control and warming (using the Mann–Whitney U-test) (A–D). PCoA analysis was performed on differences in community composition at different depths under control (E) and warming (F).

Figure 2

The correlation between nutrient variables and the diversity of bacteria in the alpine ecosystem. Heatmaps of the Spearman’s correlation coefficients between community diversity and individual nutrient variables under control (A) and warming (B). ^*p < 0.05; ^**p < 0.01. The importance of bacterial α-and β-diversity driving the cycling of soil multi-nutrient in the entire profile under control (C) and warming (D), was assessed by RF analysis.

Figure 3

Main potential bacteria contribute to soil multi-nutrient cycling in the alpine ecosystem under warming. The importance of these predictors was estimated using the percent increase in the MSE of the variables, with higher MSE% values indicating more important predictors. The p < 0.05 (*) and p < 0.01 (**) indicate significance at the levels of 5% and 1%, respectively.

Figure 4

The bacteria network and biomarkers under control and warming. (A) Microbial co-occurrence networks under control and warming. The thickness of the edges is proportional to the value of the Spearman’s correlation coefficient, and the size of the nodes is proportional to the degree of the OTUs. (B) Roles of nodes based on their Zi and Pi values in the co-occurrence networks.

Figure 5

Biomarkers of bacteria between control and warming throughout the entire profile. The top 29 biomarker bacterial OTUs were accurately identified by RF analysis in the control (A), and 32 were identified in the warming profile (B).