Site-Dependent Relationships Between Fungal Community Composition, Plant Genotypic Diversity and Environmental Drivers in a Salix Biomass System.

Stefanie Hoeber,Petra Fransson,Martin Weih,Christel Baum,Stefano Manzoni

doi:10.3389/ffunb.2021.671270

Abstract

Soil fungi are strongly affected by plant species or genotypes since plants modify their surrounding environment, but the effects of plant genotype diversity on fungal diversity and function have not been extensively studied. The interactive responses of fungal community composition to plant genotypic diversity and environmental drivers were investigated in Salix biomass systems, posing questions about: (1) How fungal diversity varies as a function of plant genotype diversity; (2) If plant genotype identity is a strong driver of fungal community composition also in plant mixtures; (3) How the fungal communities change through time (seasonally and interannually)?; and (4) Will the proportion of ECM fungi increase over the rotation? Soil samples were collected over 4 years, starting preplanting from two Salix field trials, including four genotypes with contrasting phenology and functional traits, and genotypes were grown in all possible combinations (four genotypes in Uppsala, Sweden, two in Rostock, Germany). Fungal communities were identified, using Pacific Biosciences sequencing of fungal ITS2 amplicons. We found some site-dependent relationships between fungal community composition and genotype or diversity level, and site accounted for the largest part of the variation in fungal community composition. Rostock had a more homogenous community structure, with significant effects of genotype, diversity level, and the presence of one genotype ("Loden") on fungal community composition. Soil properties and plant and litter traits contributed to explaining the variation in fungal species composition. The within-season variation in composition was of a similar magnitude to the year-to-year variation. The proportion of ECM fungi increased over time irrespective of plant genotype diversity, and, in Uppsala, the 4-mixture showed a weaker response than other combinations. Species richness was generally higher in Uppsala compared with that in Rostock and increased over time, but did not increase with plant genotype diversity. This significant site-specificity underlines the need for consideration of diverse sites to draw general conclusions of temporal variations and functioning of fungal communities. A significant increase in ECM colonization of soil under the pioneer tree Salix on agricultural soils was evident and points to changed litter decomposition and soil carbon dynamics during Salix growth.

Highlights

Fungi are principal drivers of biogeochemical cycling, linking above- and belowground ecosystem components through their roles as symbiotic mediators of plant nutrient uptake (Smith and Read, 2008), and as decomposers of litter (Schneider et al, 2012)
The number of sequences per sample varied greatly (Supplementary Figure 2), it was clear from the multivariate analyses that the rarefied and the original dataset (Figure 1, Supplementary Figures 3, 4), as FIGURE 1 | composition is visualized by (A,B) a sample plot and (C) a species plot of a principle component analysis (PCA) based on PacBio sequencing of amplified ITS2 markers
We investigated the interactive responses of soil fungal community composition to plant genotypic diversity and environmental drivers in a Salix biomass system

Summary

Introduction

Fungi are principal drivers of biogeochemical cycling, linking above- and belowground ecosystem components through their roles as symbiotic mediators of plant nutrient uptake (Smith and Read, 2008), and as decomposers of litter (Schneider et al, 2012). Soil fungal communities are strongly influenced by plant genotypes or species (Prescott and Grayston, 2013; Gallart et al, 2018b), since plants modify their surrounding environment (De Deyn et al, 2008), for example by providing living and dead organic matter, and by feeding soil microbial communities via rhizodeposition (Steinauer et al, 2016) All these plant-derived substrates are likely to be affected by plant genotypes, species, and diversity (Weih and Nordh, 2002; Hoeber et al, 2020). The relationships between plant diversity and ecosystem functions are complex (Gamfeldt et al, 2013; van der Plas et al, 2016; Baeten et al, 2019), but because of the interactions between fungi and plants, these relationships are likely mediated and possibly explained by the composition and function of soil fungi In this contribution, we explore the links between fungal communities and plant genotype diversity. Many previous studies were conducted on seedlings or younger trees; the extent to which variation in tree genetics influences the structure and function of fungal communities within populations of adult trees remains an open question

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