RT Journal Article SR Electronic T1 Soil microbial communities associated with giant sequoia: How does the world’s largest tree affect some of the world’s smallest organisms? JF bioRxiv FD Cold Spring Harbor Laboratory SP 807040 DO 10.1101/807040 A1 Chelsea J. Carey A1 Sydney I. Glassman A1 Thomas D. Bruns A1 Emma L. Aronson A1 Stephen C. Hart YR 2019 UL http://biorxiv.org/content/early/2019/10/17/807040.abstract AB Giant sequoia (Sequoiadendron giganteum) is an iconic conifer that lives in relic 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 extends more broadly to non-mycorrhizal components of the soil microbial community. To address this question we characterized microbiomes associated with giant sequoia and co-occurring sugar pine (Pinus lambertiana) by sequencing 16S and ITS1 of the bulk soil community at two groves with distinct parent material. 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 unique core community that was 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, calcium availability, 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.