Contrasting Responses of Rhizosphere Bacteria, Fungi and Arbuscular Mycorrhizal Fungi Along an Elevational Gradient in a Temperate Montane Forest of China.

Yaoxin Guo,Fazhu Zhao,Russell Doughty,Junjie Yi,Chengjie Ren

doi:10.3389/fmicb.2020.02042

Abstract

Elevational gradients strongly affect microbial biodiversity in bulk soil through altering plant and soil properties, but the effects on rhizosphere microbial patterns remain unclear, especially at large spatial scales. We therefore designed an elevational gradient experiment to examine rhizosphere microbial (bacteria, fungi and arbuscular mycorrhizal fungi) diversity and composition using Illumina sequencing of the 16S rRNA and ITS genes for comparison to plant and soil properties. Our results showed that bacterial and fungal alpha diversity was significantly higher at mid-elevation, while AMF alpha diversity decreased monotonically. The beta diversities of the three groups were significantly affected by elevational gradients, but the effect on bacterial beta diversity was larger than on fungal and AMF beta diversity. Proteobacteria, the dominant phyla of bacteria, was significantly higher at the mid-elevation, while Acidobacteria and Actinobacteria significantly decreased as elevation increased. The main fungal taxa, Basidiomycota, significantly decreased with elevation, and Ascomycota significantly increased with elevation. Glomeromycota, the dominant AMF phyla, responded insignificantly to the elevational gradients. The responses of bacterial and fungal alpha diversity were mostly associated with tree diversity and organic carbon, whereas AMF alpha diversity mainly depended on litter N and P. Changes in bacterial community composition along the elevational gradient were explained primarily by litter N and P, and litter P was the main driver of fungal and AMF community composition. Overall, our results suggest that plant litter, particularly litter N and P, were the main source of external carbon input and drove the observed differences in rhizosphere microbial diversity and community composition. Our results highlight the importance of litter nutrition in structuring rhizosphere microbial communities in mountain ecosystems.

Highlights

In mountain ecosystems, many climate factors can vary drastically over a short spatial distance, which influence aboveground macroorganisms and microorganisms belowground (Fierer et al, 2011; Sundqvist et al, 2013)
By studying the rhizosphere microbial community and corresponding plant and soil properties along a 1300 m elevational range on Taibai Mountain, a global biodiversity hot spot, we found that rhizosphere microbial diversity changed significantly along the elevational gradient depending on plant and soil properties
We found different responses of rhizosphere microbial diversity and community composition to elevational gradient depending on plant and soil properties

Summary

Introduction

Many climate factors can vary drastically over a short spatial distance (see review by Körner, 2007), which influence aboveground macroorganisms and microorganisms belowground (Fierer et al, 2011; Sundqvist et al, 2013). A variety of studies have investigated the response of microbial community in bulk soil to elevational gradients, suggesting that elevational gradients strongly affect the microbial diversity and community composition of bulk soils by altering plant and soil characteristics (Meng et al, 2013; Li et al, 2018; Saitta et al, 2018). In such dynamic environments,the shift of the microbial community in bulk soil and its interaction with plants, plant roots, can potentially alter rhizosphere microorganisms. The lack of research in this area greatly hinders our predictions of nutrient cycling of terrestrial ecosystem under climate warming, despite the importance of rhizosphere microorganisms in mediating biogeochemical cycles (Van der Heijden et al, 2008; Delgado-Baquerizo et al, 2016)

Methods

Results

Discussion

Conclusion