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Title: Plant root exudates increase methane emissions through direct and indirect pathways

Abstract

We report that the largest natural source of methane (CH4) to the atmosphere is wetlands, which produce 20% to 50% of total global emissions. Vascular plants play a key role regulating wetland CH4 emissions through multiple mechanisms. They often contain aerenchymatous tissues which act as a diffusive pathway for CH4 to travel from the anoxic soil to the atmosphere and for O2 to diffuse into the soil and enable methanotrophy. Plants also exude carbon from their roots which stimulates microbial activity and fuels methanogenesis. This study investigated these mechanisms in a laboratory experiment utilizing rootboxes containing either Carex aquatilis plants, silicone tubes that simulated aerenchymatous gas transfer, or only soil as a control. CH4 emissions were over 50 times greater from planted boxes than from control boxes or simulated plants, indicating that the physical transport pathway of aerenchyma was of little importance when not paired with other effects of plant biology. Plants were exposed to 13CO2 at two time-points and subsequent enrichment of root tissue, rhizosphere soil, and emitted CH4 was used in an isotope mixing model to determine the proportion of plant-derived versus soil-derived carbon supporting methanogenesis. Results showed that carbon exuded by plants was converted to CH4 butmore » also that planted boxes emitted 28 times more soil-derived carbon than the other experimental treatments. At the end of the experiment, emissions of excess soil-derived carbon from planted boxes exceeded the emission of plant-derived carbon. Finally, this result signifies that plants and root exudates altered the soil chemical environment, increased microbial metabolism, and/or changed the microbial community such that microbial utilization of soil carbon was increased (e.g. microbial priming) and/or oxidation of soil-derived CH4 was decreased (e.g., by microbial competition for oxygen).« less

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of Washington, Seattle, WA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Univ. of Washington, Seattle, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS)
OSTI Identifier:
1598837
Grant/Contract Number:  
SC0010338; AC05-76RL01830; SC0014664
Resource Type:
Accepted Manuscript
Journal Name:
Biogeochemistry
Additional Journal Information:
Journal Volume: 145; Journal Issue: 1-2; Journal ID: ISSN 0168-2563
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Methane; Wetlands; Microbial priming; Root exudates; Climate change

Citation Formats

Waldo, Nicholas B., Hunt, Brianna K., Fadely, Eleanor C., Moran, James J., and Neumann, Rebecca B. Plant root exudates increase methane emissions through direct and indirect pathways. United States: N. p., 2019. Web. https://doi.org/10.1007/s10533-019-00600-6.
Waldo, Nicholas B., Hunt, Brianna K., Fadely, Eleanor C., Moran, James J., & Neumann, Rebecca B. Plant root exudates increase methane emissions through direct and indirect pathways. United States. https://doi.org/10.1007/s10533-019-00600-6
Waldo, Nicholas B., Hunt, Brianna K., Fadely, Eleanor C., Moran, James J., and Neumann, Rebecca B. Thu . "Plant root exudates increase methane emissions through direct and indirect pathways". United States. https://doi.org/10.1007/s10533-019-00600-6. https://www.osti.gov/servlets/purl/1598837.
@article{osti_1598837,
title = {Plant root exudates increase methane emissions through direct and indirect pathways},
author = {Waldo, Nicholas B. and Hunt, Brianna K. and Fadely, Eleanor C. and Moran, James J. and Neumann, Rebecca B.},
abstractNote = {We report that the largest natural source of methane (CH4) to the atmosphere is wetlands, which produce 20% to 50% of total global emissions. Vascular plants play a key role regulating wetland CH4 emissions through multiple mechanisms. They often contain aerenchymatous tissues which act as a diffusive pathway for CH4 to travel from the anoxic soil to the atmosphere and for O2 to diffuse into the soil and enable methanotrophy. Plants also exude carbon from their roots which stimulates microbial activity and fuels methanogenesis. This study investigated these mechanisms in a laboratory experiment utilizing rootboxes containing either Carex aquatilis plants, silicone tubes that simulated aerenchymatous gas transfer, or only soil as a control. CH4 emissions were over 50 times greater from planted boxes than from control boxes or simulated plants, indicating that the physical transport pathway of aerenchyma was of little importance when not paired with other effects of plant biology. Plants were exposed to 13CO2 at two time-points and subsequent enrichment of root tissue, rhizosphere soil, and emitted CH4 was used in an isotope mixing model to determine the proportion of plant-derived versus soil-derived carbon supporting methanogenesis. Results showed that carbon exuded by plants was converted to CH4 but also that planted boxes emitted 28 times more soil-derived carbon than the other experimental treatments. At the end of the experiment, emissions of excess soil-derived carbon from planted boxes exceeded the emission of plant-derived carbon. Finally, this result signifies that plants and root exudates altered the soil chemical environment, increased microbial metabolism, and/or changed the microbial community such that microbial utilization of soil carbon was increased (e.g. microbial priming) and/or oxidation of soil-derived CH4 was decreased (e.g., by microbial competition for oxygen).},
doi = {10.1007/s10533-019-00600-6},
journal = {Biogeochemistry},
number = 1-2,
volume = 145,
place = {United States},
year = {2019},
month = {9}
}

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