Do temperate tree species diversity and identity influence soil microbial community function and composition?

Alain Paquette,Peter B. Reich,Christian Messier,Rim Khlifa,Alison D. Munson

doi:10.1002/ece3.3313

Abstract

Studies of biodiversity–ecosystem function in treed ecosystems have generally focused on aboveground functions. This study investigates intertrophic links between tree diversity and soil microbial community function and composition. We examined how microbial communities in surface mineral soil responded to experimental gradients of tree species richness (SR), functional diversity (FD), community‐weighted mean trait value (CWM), and tree identity. The site was a 4‐year‐old common garden experiment near Montreal, Canada, consisting of deciduous and evergreen tree species mixtures. Microbial community composition, community‐level physiological profiles, and respiration were evaluated using phospholipid fatty acid (PLFA) analysis and the MicroResp™ system, respectively. The relationship between tree species richness and glucose‐induced respiration (GIR), basal respiration (BR), metabolic quotient (qCO 2) followed a positive but saturating shape. Microbial communities associated with species mixtures were more active (basal respiration [BR]), with higher biomass (glucose‐induced respiration [GIR]), and used a greater number of carbon sources than monocultures. Communities associated with deciduous tree species used a greater number of carbon sources than those associated with evergreen species, suggesting a greater soil carbon storage capacity. There were no differences in microbial composition (PLFA) between monocultures and SR mixtures. The FD and the CWM of several functional traits affected both BR and GIR. In general, the CWM of traits had stronger effects than did FD, suggesting that certain traits of dominant species have more effect on ecosystem processes than does FD. Both the functions of GIR and BR were positively related to aboveground tree community productivity. Both tree diversity (SR) and identity (species and functional identity—leaf habit) affected soil microbial community respiration, biomass, and composition. For the first time, we identified functional traits related to life‐history strategy, as well as root traits that influence another trophic level, soil microbial community function, via effects on BR and GIR.

Highlights

Faced with an accelerated decline in biodiversity and the challenge of maintaining the provision of ecosystem goods and services, the last two decades witnessed a growing number of studies exploring the links between diversity and ecosystem functions (BEF), with an emphasis on species richness (SR) and on productivity as the measured function
We observed that the function of the soil microbial community responded to species richness (SR), but that the structure and composition did not (Phospholipid fatty acid extraction, phospholipid fatty acid (PLFA))
This is the first tree diversity experiment to isolate the effects of tree species richness (SR) and functional diversity (FD) on soil microbial community function (GIR—a proxy of microbial biomass—biomass (GIR) and respiration (BR) and qCO2)

Summary

Introduction

Faced with an accelerated decline in biodiversity and the challenge of maintaining the provision of ecosystem goods and services, the last two decades witnessed a growing number of studies exploring the links between diversity (of different organisms) and ecosystem functions (BEF), with an emphasis on species richness (SR) and on productivity as the measured function. A positive relationship between diversity and productivity was demonstrated in grasslands, aquatic systems, bacterial microcosms, and soil communities (Cardinale et al, 2011, 2012; Hooper et al, 2012; Reich et al, 2012), generally showing a saturating shape indicating functional redundancy (Liang et al, 2016; O’Connor et al, 2017). The different mechanisms by which plant diversity or identity influence ecosystem functioning are still poorly understood, especially in the belowground compartment. As soil microbial communities are major drivers of local and global biogeochemical cycles (Van Der Heijden, Bardgett, & Van Straalen, 2008; Wardle et al, 2004), it is important to investigate by which mechanisms plant species diversity and identity may influence both microbial community structure and functions such as basal respiration

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