Temporal changes and alternating host tree root and shoot growth affect soil microbiomes

Jean De Dieu Habiyaremye,Sylvie Herrmann,François Buscot,Kezia Goldmann

doi:10.3390/ecm2020-07109

Abstract

Patterns of trees’ endogenous rhythmic growth (ERG) and paralleled C allocation shift between root and shoot systems have been studied, but there is still a need to understand their impact in shaping soil microbiomes. Moreover, impact of plants on soil microbial communities can be modulated or overweighed by time-induced plant and/or seasonal changes. Thus, we intended to analyze the structure of soil microbiomes as response to simultaneous alternated host tree root and shoot flushes and time-induced changes within one vegetation period at two sites in Central Germany. In this study, we utilized oak phytometers (Quercus robur L., clone DF159) as host trees, and made use of their ERG, whereby consecutive root and shoot flushes make a complete growth cycle. We studied two complete growth cycles during the same vegetation period, performed a non-destructive soil sampling and applied high-throughput amplicon sequencing of the bacterial 16S gene and the fungal ITS2 region. As C allocation shifts between the tree root and shoot, released root exudates and consequently the nutrient availability alternate for soil microorganisms. We therefore anticipated different microbial communities in the host tree root zone along the growth cycles until senescence. In our results, the bacterial community exhibited a directional change over time along the vegetation period. In contrast, the fungal community appeared sample specific. Our findings enlarge the current understanding of the temporal microbial assembly in the host tree root zone.

Highlights

Plant-root associated microorganisms feed primarily on plant rhizodeposits [1], of which the amount and dynamics are correlated with plant biomass [2]
We studied two complete growth cycles during the same vegetation period, performed a nondestructive soil sampling and applied high-throughput amplicon sequencing of the bacterial 16S gene and the fungal ITS2 region
From both the non-metric multidimensional scaling (NMDS) plot and PERMANOVA results, bacterial community of the tree root and root-free zones changed between time points along a vegetation period (p

Summary

Introduction

Plant-root associated microorganisms feed primarily on plant rhizodeposits [1], of which the amount and dynamics are correlated with plant biomass [2]. Oak trees (Quercus robur L.) are characterized by an endogenous rhythmic growth (ERG) with an alternation of root flush (RF) and shoot flush (SF), which are constitutive of one rhythmic growth cycle [4]. This alternation can be followed by using anatomical shoot bud developmental stages from A to D [5]: bud resting for stage A indicates the end of a SF; bud swelling for stage B corresponds to ongoing RF; bud outbusting for stage C indicates the end of a RF; and leaf expansion from the bud known as stage D corresponds to a new SF. This should induce changes in the tree root associated microbial communities

Methods

Results

Conclusion