The Abundance of the nifH Gene Became Higher and the nifH-Containing Diazotrophic Bacterial Communities Changed During Primary Succession in the Hailuogou Glacier Chronosequence, China.

Yingyan Wang,Xiumei Yu,Petri Penttinen,Hao Jiang,Ke Zhao,Quanju Xiang,Yunfu Gu,Yulan Chen,Qinyu Xue,Xiaoping Zhang,Qiang Chen,Menggen Ma

doi:10.3389/fmicb.2021.672656

Abstract

Primary successional ecosystems and the related soil development are often N limited. To date, N2-fixing communities during primary succession in alpine ecosystems have remained underexplored. In this study, we applied quantitative PCR (qPCR) quantitation and targeted amplicon sequencing of nifH in the Hailuogou Glacier foreland to investigate the succession of N2-fixing communities in five sites along a 62-year chronosequence. The abundance of the nifH gene increased along the primary succession in the chronosequence and correlated positively with pH, acetylene reduction activity, and water, organic C, total and available N, and available P contents. The increases in alpha diversity along the chronosequence may have been partly due to less competition for resources. In contrast to the clear separation based on soil properties, the changes in the diazotrophic community composition lacked a clear trend and were associated mostly with changes in soil available K and organic C contents. The changes among differentially abundant genera were possibly due to the changes in plant coverage and species composition. The whole primary succession of the diazotrophic communities was consistent with stochastic community assembly, which is indicative of low competitive pressure.

Highlights

The first steps of primary succession in recently exposed environments, for example, after glacier retreat, include colonization by pioneer communities and nutrient mobilization (Odum, 1969)
Our aims were to analyze N2-fixing communities and changes in them during primary succession, to identify the specific taxa that characterize the changes, and to determine soil parameters associated with these changes
Five eGENs and six dGENs were detected between BJ and T0 (Figure 3A), five eGENs and six dGENs between T1 and T2 (Figure 3C), and three eGENs between T2 and T3 (Figure 3D)

Summary

Introduction

The first steps of primary succession in recently exposed environments, for example, after glacier retreat, include colonization by pioneer communities and nutrient mobilization (Odum, 1969). The glacier retreat provides ideal models for Hailuogou Glacier Chronosequence: N2-Fixing Microorganism exploring soil primary succession; the exposed, originally barren land goes through a succession of soil processes, including carbon (C) and nitrogen (N) accumulation, transformation, and nutrient cycling (Hopkins et al, 2007; Nemergut et al, 2007). The soil microorganisms play an important role in mediating these processes. By focusing on the soil microorganisms, the period needed to decipher the community development patterns in primary succession will be considerably shorter than when studying plant or animal communities (Jessup et al, 2004)

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