Plant-mycorrhizal-decomposer interactions and their impacts on terrestrial biogeochemistry

POLICELLI NAHUEL; AVERILL, COLIN; BRZOSTEK, EDWARD; LIAO, HUI-LING; CHEN, KO-HSUAN; TAPPERO, RYAN; CARRARA, JOSEPH; VIETORISZ, CORINNE; NASH, JAKE; VILGALYS, RYTAS; BHATNAGAR, JENNIFER M.

Salt Lake City - Virtual

Congreso; ESA 2020 - Meeting of the Ecological Society of America; 2020

Ecological Society of America

Interactions between soil microbes can drastically alter ecosystem processesboth above and belowground, but the mechanisms by which these microbesinteract, and their impacts on soil biogeochemistry remain elusive. Weaimed to characterize interactions between coniferous plants, their majorroot fungal symbionts (ectomycorrhizal fungi, EMF), and free-livingsaprotrophic decomposers (SAPs) in soil along gradients in resourceavailability. We performed a greenhouse-based synthetic ecosystemexperiment with Pinus taeda seedlings growing with and without their EMFsymbiont (Suillus cothurnatus), under high and low levels of soil carbon (C),soil nitrogen (N), and plant C (ambient vs. elevated carbon dioxide -CO ). Weexpected that under low soil C, EMF prime decomposer activity and increasethe release of soil C as CO , while under high soil C, EMF slow decompositionand reduce soil CO release, with EMF competing with SAPs for access to soilorganic matter (i.e. the Gadgil effect). These processes would be exacerbatedunder high plant C availability to EMF, but suppressed under high soil N.We found that EMF prime decay of soil organic matter under low soil C, butslow decay under high soil C. Elevated soil N suppressed the EMF effect onsoil C-derived CO losses. Under elevated CO , soil CO release was always higher with more soil C. There was a tendency for greater soil CO release when N was added to soils with high soil C in the presence of EMF, although we didn?t find strong evidence of this pattern. Together, our results suggest that the direction of EMF-SAP interactions is highly dependent on soil C and N availability to SAPs and might change according to plant C level.