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Title: Plant roots stimulate the decomposition of complex, but not simple, soil carbon

Abstract

Roots release carbon into soil and can alleviate energy limitation of microbial organic matter decomposition. We know little about the effects of roots on microbial decomposition of different organic matter substrates, despite the importance for soil carbon stocks and turnover. Through implementing root-microbe interactions, the Carbon, Organisms, Rhizosphere, and Protection in the Soil Environment (CORPSE) model was previously shown to represent dynamics of total soil carbon in temperate forest field experiments. However, the model permits alternative hypotheses concerning microbial-substrate affinity. We investigated how root inputs affect decomposition of soil organic carbon (SOC) with variable decomposability. We simulated SOC stocks in CORPSE and compared microbial degradation of two substrates types with varying root-microbe interactions under two alternative hypotheses that varied in microbial-substrate affinity. We compared our modeled hypotheses to a forest field experiment where we quantified decomposition of isotopically-labeled starch and leaf tissues in soils with manipulated root access to microbes. Here, we tested the hypothesis that decomposition of leaves would be more sensitive to root inputs than decomposition of starch, corresponding to the alternative model hypothesis. In the field study, leaf decomposition increased with root density while starch decomposition was unchanged by root density. Microbial biomass and enzyme activity consistentlymore » increased with root inputs in CORPSE and the field study. Our field experiment supported the CORPSE simulations with high microbial-substrate affinity. Roots stimulated microbial growth and enzyme production, which increased degradation of more complex substrates such as leaf tissues. Substrates that were easily decomposed, such as starch, may already be degrading at a maximum rate in the absence of rhizosphere influence because their decomposition rate was unchanged by root inputs. We found that the degree to which roots stimulate microbial decomposition depends on the substrate being decomposed, and that root-microbe interactions influenced SOC stocks in both our model and field experiment. Environmental changes that alter root-microbe interactions could, therefore, alter soil C stocks and biogeochemical cycling, and models of these interactions should incorporate differential influence of rhizosphere inputs on different substrates.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2];  [3];  [4]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Univ. of Tennessee, Knoxville, TN (United States)
  4. Univ. of Vermont, Burlington, VT (United States)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1609047
Alternate Identifier(s):
OSTI ID: 1582681
Grant/Contract Number:  
AC05-00OR22725; SC0010562
Resource Type:
Accepted Manuscript
Journal Name:
Functional Ecology
Additional Journal Information:
Journal Volume: 34; Journal Issue: 4; Journal ID: ISSN 0269-8463
Publisher:
British Ecological Society; Wiley
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; broadleaf boreal forest; ecosystem model; extracellular enzymes; plant-microbe interaction; soil carbon; soil organic matter; stable isotopes

Citation Formats

Moore, Jessica, Sulman, Benjamin, Mayes, Melanie A., Patterson, Courtney M., and Classen, Aimee T. Plant roots stimulate the decomposition of complex, but not simple, soil carbon. United States: N. p., 2019. Web. doi:10.1111/1365-2435.13510.
Moore, Jessica, Sulman, Benjamin, Mayes, Melanie A., Patterson, Courtney M., & Classen, Aimee T. Plant roots stimulate the decomposition of complex, but not simple, soil carbon. United States. https://doi.org/10.1111/1365-2435.13510
Moore, Jessica, Sulman, Benjamin, Mayes, Melanie A., Patterson, Courtney M., and Classen, Aimee T. Thu . "Plant roots stimulate the decomposition of complex, but not simple, soil carbon". United States. https://doi.org/10.1111/1365-2435.13510. https://www.osti.gov/servlets/purl/1609047.
@article{osti_1609047,
title = {Plant roots stimulate the decomposition of complex, but not simple, soil carbon},
author = {Moore, Jessica and Sulman, Benjamin and Mayes, Melanie A. and Patterson, Courtney M. and Classen, Aimee T.},
abstractNote = {Roots release carbon into soil and can alleviate energy limitation of microbial organic matter decomposition. We know little about the effects of roots on microbial decomposition of different organic matter substrates, despite the importance for soil carbon stocks and turnover. Through implementing root-microbe interactions, the Carbon, Organisms, Rhizosphere, and Protection in the Soil Environment (CORPSE) model was previously shown to represent dynamics of total soil carbon in temperate forest field experiments. However, the model permits alternative hypotheses concerning microbial-substrate affinity. We investigated how root inputs affect decomposition of soil organic carbon (SOC) with variable decomposability. We simulated SOC stocks in CORPSE and compared microbial degradation of two substrates types with varying root-microbe interactions under two alternative hypotheses that varied in microbial-substrate affinity. We compared our modeled hypotheses to a forest field experiment where we quantified decomposition of isotopically-labeled starch and leaf tissues in soils with manipulated root access to microbes. Here, we tested the hypothesis that decomposition of leaves would be more sensitive to root inputs than decomposition of starch, corresponding to the alternative model hypothesis. In the field study, leaf decomposition increased with root density while starch decomposition was unchanged by root density. Microbial biomass and enzyme activity consistently increased with root inputs in CORPSE and the field study. Our field experiment supported the CORPSE simulations with high microbial-substrate affinity. Roots stimulated microbial growth and enzyme production, which increased degradation of more complex substrates such as leaf tissues. Substrates that were easily decomposed, such as starch, may already be degrading at a maximum rate in the absence of rhizosphere influence because their decomposition rate was unchanged by root inputs. We found that the degree to which roots stimulate microbial decomposition depends on the substrate being decomposed, and that root-microbe interactions influenced SOC stocks in both our model and field experiment. Environmental changes that alter root-microbe interactions could, therefore, alter soil C stocks and biogeochemical cycling, and models of these interactions should incorporate differential influence of rhizosphere inputs on different substrates.},
doi = {10.1111/1365-2435.13510},
journal = {Functional Ecology},
number = 4,
volume = 34,
place = {United States},
year = {Thu Dec 12 00:00:00 EST 2019},
month = {Thu Dec 12 00:00:00 EST 2019}
}

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Cited by: 22 works
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