Root-Mediated Impacts of Plant Volatile Organic Compound Emissions on Soil Carbon
Linnea Honeker1* (email@example.com), Holly Andrews1, Manjula Canagaratna2, Elizabeth Lunny2, Juliana Gil-Loaiza1, Malak M. Tfaily1, Jordan Krechmer2, Megan Claflin2, J. Rob Roscioli2, Joanne Shorter2, Duke Pauli1, Jeffrey Demieville1, Meara Clark1, Justin Grigory1, Robert Stanley3, Dusan Velickovic3, David Hoyt3, Robert Young3, Chaevien Clendinen3, Kolby Jardine4, Romy Chakraborty4, Margaret Torn4, Eoin Brodie4, and Laura K. Meredith1
1University of Arizona; 2Aerodyne Research, Inc.; 3Pacific Northwest National Laboratory; and 4Lawrence Berkeley National Laboratory
The overarching project goal is to verify and quantify volatile organic compounds (VOCs) as direct and indirect contributors to soil C stabilization within the rhizosphere and beyond through teleconnections in the soil matrix, and to determine their underpinning ecological and metabolic mechanisms. The long-term motivation for the project is to transform the current conceptual understanding and predictive capacity of microbial systems and soil C stabilization to include the important roles of volatile compounds. This presentation falls under the objective to determine the direct pathways and contributions of root-released VOCs and VOC transformations by soil microbiomes to soil C cycling and stabilization. Specifically, in this task, researchers will aim to identify VOC-consuming microbes and traits and identify pathway(s) for VOC-C stabilization in soil pools using soil incubations and time-resolved 13C-VOC stable isotope labeling.
Plants are recognized as the dominant source of VOCs to the atmosphere, where they play critical roles in air quality and climate, yet the parallel impact of plant-derived VOCs on the pedosphere (soil) remains poorly quantified. VOCs released by decomposing litter can contribute to soil carbon (C) pools including those associated with soil C stabilization, and researchers hypothesize that root VOCs can also contribute to these soil C pools. Furthermore, researchers anticipate that this pathway for soil C stabilization will depend on plant physiological traits, rhizosphere microbes and their activity, and soil environmental factors.
While the composition and flux of root-soil emissions of VOCs in the rhizosphere remain poorly quantified due to the lack of developed methods, here the team characterized the belowground release of plant VOCs to the soil system in two distinct ecosystems. Beneath the bioenergy relevant crop sorghum in a semi-arid agroecosystem at the Maricopa Agriculture Center in AZ, the team quantified soil VOC concentrations (proton transfer reaction time of flight mass spectrometer interfaced with novel in situ diffusion gas probes; Roscioli et al. 2021; Gil-Loaiza et al. 2022) and root metabolites (nuclear magnetic resonance; NMR) to identify root VOCs and estimate their potential in situ uptake rates in soil. In addition, the team leveraged an experimental soil warming treatment in the temperate coniferous Blodgett Experimental Forest in the Sierra Foothills in CA to explore associations between regions of root growth, increased VOC concentrations (NMR), and enhanced soil organic carbon (SOC) stocks. In bulk surface soils, researchers observed increases in both SOC stock and VOC concentrations including ethanol and methanol. Together, these field observations help to begin to define the contributions of root VOCs to soil C stabilization. They also serve as a reference for upcoming experimental tests of the impact of plant traits and environmental conditions on this under-resolved C transformation pathway.
Figure 1. Illustration of the overarching project goal to verify and quantify volatile organic compounds (VOCs) as direct and indirect contributors to soil C stabilization within the rhizosphere and beyond through teleconnections, and to determine their underpinning ecological and metabolic mechanisms.
Roscioli, J. R., et al. 2021. “Soil Gas Probes for Monitoring Trace Gas Messengers of Microbial ” Scientific Reports 11(1), 8327.
Gil-Loaiza, J., et al. 2022. “Versatile Soil Gas Concentration and Isotope Monitoring: Optimization and Integration of Novel Soil Gas Probes with Online Trace Gas Detection.” Biogeosciences 19(1), 165–85.
This research was supported by the DOE Office of Science, Office of Biological and Environmental Research (BER), grant nos. DE-SC0023189 and DE-SC0018459, A portion of this research was performed on a project award 10.46936/fics.proj.2021.60045/60000398 under the FICUS program and used resources at the DOE Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility sponsored by the BER program and operated under Contract No. DE-AC05-76RL01830. Part of this work was also performed at Lawrence Berkeley National Laboratory supported by the U.S. Department of Energy, Office of Science, Office of BER under Contract No. DE-AC02-05CH11231.