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

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.

Mega-fire in Redwood Tanoak Forest Reduces Bacterial and Fungal Richness and Selects for Pyrophilous Taxa and Traits that are Phylogenetically Conserved

“…A couple recent studies have found an increase in dominance of the sister genus Geminibasidium, including a study of a Pinus ponderosa forest in the American Pacific Northwest (Pulido-Chavez et al, 2021) and a study of Larix and Betula dominated forests in northeastern China (Yang et al, 2020). Geminibasidium was also present at 0.05% sequence abundance, the same amount as our pre-fire soil, in an unburned giant sequoia forest (Carey et al, 2019). While Geminibasidiomycetes are positively selected for by fire Mega-Fire Effect on Pyrophilous Microbes 23 (Figure 6) likely due to their thermotolerance and xerotolerance (Nguyen et al, 2013), they have been missed by existing descriptions of pyrophilous fungi that are mainly based on fruiting body 504 surveys (McMullan-Fisher et al, 2011).…”

“…Additionally, a study of the microbial composition of the coastal redwood's sister genus, the giant sequoia (Sequoiadendron giganteum), also showed domination by Bradyrhizobium and Sinobacteraceae sp. of the Proteobacteria (Carey et al, 2019). The similarities with the giant sequoia soil communities also extend to fungi, with Hygrocybe 487 dominating both our redwood forests pre-fire and in the giant sequoia forest.…”

Keep your friends close: Host compartmentalisation of microbial communities facilitates decoupling from effects of habitat fragmentation

“…We identified 357 potential ectomycorrhizal fungi (EMF) and 25 ericoid mycorrhizal OTUs throughout this study based on FUNGUILD delineations of 'highly probable' and 'probable' matches (Nguyen et al, 2016) and of these, 206 (approximately 58%) EMF OTUs were found in association with roots at low, but consistent relative abundance (Figure S6). Similar reports have been recorded in other studies where EMF are found associated with nonhost species (Carey et al, 2020;Dawkins & Esiobu, 2017;Schneider-Maunoury et al, 2020) and the 'waiting-room' hypothesis, where the ectomycorrhizal habit evolved from fungal endophytes, has been posited as an explanation (Selosse et al, 2009(Selosse et al, , 2018Smith et al, 2017).…”

Rapid bacterial and fungal successional dynamics in first year after Chaparral wildfire

“…In our system, phosphate was significantly lower in the burned sites (data not shown), thus potentially explaining the fruiting of Coprinellus at later successional stages. Moreover, in support of recent studies in pine forests (Carey et al, 2020;Enright et al, 2021;Pulido-Chavez et al, 2021), we found Geminibasidium in our burned soils. Geminibasidium is a recently described thermotolerant saprobe (H. D. T. Nguyen et al, 2013) that was not present in the unburned sites but dominated early successional stages.…”