Soil microbial communities associated with giant sequoia: How does the world's largest tree affect some of the world's smallest organisms?

Chelsea J Carey,Thomas D Bruns,Sydney I Glassman,Stephen C Hart,Emma L Aronson

doi:10.1002/ece3.6392

Abstract

Giant sequoia (Sequoiadendron giganteum) is an iconic conifer that lives in relict populations on the western slopes of the California Sierra Nevada. In these settings, it is unusual among the dominant trees in that it associates with arbuscular mycorrhizal fungi rather than ectomycorrhizal fungi. However, it is unclear whether differences in microbial associations extend more broadly to nonmycorrhizal components of the soil microbial community. To address this question, we used next‐generation amplicon sequencing to characterize bacterial/archaeal and fungal microbiomes in bulk soil (0–5 cm) beneath giant sequoia and co‐occurring sugar pine (Pinus lambertiana) individuals. We did this across two groves with distinct parent material in Yosemite National Park, USA. We found tree‐associated differences were apparent despite a strong grove effect. Bacterial/archaeal richness was greater beneath giant sequoia than sugar pine, with a core community double the size. The tree species also harbored compositionally distinct fungal communities. This pattern depended on grove but was associated with a consistently elevated relative abundance of Hygrocybe species beneath giant sequoia. Compositional differences between host trees correlated with soil pH and soil moisture. We conclude that the effects of giant sequoia extend beyond mycorrhizal mutualists to include the broader community and that some but not all host tree differences are grove‐dependent.

Highlights

There is increasing evidence that tree species influence a combination of soil chemical, physical, and biological properties (Hobbie et al, 2007; Mitchell, Campbell, Chapman, & Cameron, 2010; Zheng, Wei, & Zhang, 2017)
ectomycorrhizal fungi (EMF) communities were relatively more abundant beneath sugar pine, with EMF taxa such as an unidentified Byssocorticium species tending to be more frequent and relatively abundant beneath this host tree species. While this is to be expected, our findings show that differences in mycorrhizal communities in mixed stands of arbuscular mycorrhizal fungi (AMF) and EMF trees can be seen at the bulk soil scale, which can have cascading effects on biogeochemical processes including the cycling of C (Averill, Dietze, & Bhatnagar, 2018) and N (Mushinski et al, 2019)
Using next-generation amplicon sequencing, we show for the first time that microbial communities of bulk soil differ between giant sequoia and co-occurring sugar pine

Summary

Introduction

There is increasing evidence that tree species influence a combination of soil chemical, physical, and biological properties (Hobbie et al, 2007; Mitchell, Campbell, Chapman, & Cameron, 2010; Zheng, Wei, & Zhang, 2017). Under some circumstances, direct association with host-specific symbiotic microorganisms such as mycorrhizal fungi can further promote distinct soil fungal communities (Gao et al, 2013; Urbanová, Šnajdr, & Baldrian, 2015) Such plant-induced changes to microbial communities can become more or less pronounced with time since plant establishment (Strayer, Eviner, Jeschke, & Pace, 2006), and can feed back on soil chemical and physical properties (Falkowski, Fenchel, & Delong, 2008), plant performance (Aponte, García, & Marañón, 2013; Bever et al, 2010), plant phenology (Wagner et al, 2014), and plant community composition (Van der Heijden, Bardgett, & Straalen, 2008)

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