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Title: Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations

Abstract

Terrestrial carbon (C)-climate feedbacks depend strongly on how soil organic matter (SOM) decomposition responds to temperature. This dependency is often represented in land models by the parameter Q10, which quantifies the relative increase of microbial soil respiration per 10 °C temperature increase. Many studies have conducted paired laboratory soil incubations and inferred “active” and “slow” pool Q10 values by fitting linear two-pool models to measured respiration time series. Using a recently published incubation study (Qin et al. in Sci Adv 5(7):eaau1218, 2019) as an example, here we first show that the very high parametric equifinality of the linear two-pool models may render such incubation-based Q10 estimates unreliable. In particular, we show that, accompanied by the uncertain initial active pool size, the slow pool Q10 can span a very wide range, including values as high as 100, although all parameter combinations are producing almost equally good model fit with respect to the observations. This result is robust whether or not interactions between the active and slow pools are considered (typically these interactions are not considered when interpreting incubation data, but are part of the predictive soil carbon models). This very large parametric equifinality in the context of interpreting incubation data is consistentmore » with the poor temporal extrapolation capability of linear multi-pool models identified in recent studies. Next, using a microbe-explicit SOM model (RESOM), we show that the inferred two pools and their associated parameters (e.g., Q10) could be artificial constructs and are therefore unreliable concepts for integration into predictive models. We finally discuss uncertainties in applying linear two-pool (or more generally multiple-pool) models to estimate SOM decomposition parameters such as temperature sensitivities from laboratory incubations. We also propose new observations and model structures that could enable better process understanding and more robust predictive capabilities of soil carbon dynamics.« less

Authors:
ORCiD logo; ORCiD logo
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1630347
Alternate Identifier(s):
OSTI ID: 1760256
Grant/Contract Number:  
DE‐AC02‐05CH11231; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Biogeochemistry
Additional Journal Information:
Journal Name: Biogeochemistry Journal Volume: 149 Journal Issue: 3; Journal ID: ISSN 0168-2563
Publisher:
Springer Science + Business Media
Country of Publication:
Netherlands
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Temperature sensitivity; soil respiration; laboratory incubation; two-pool models; equifinality

Citation Formats

Tang, Jinyun, and Riley, William J. Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations. Netherlands: N. p., 2020. Web. doi:10.1007/s10533-020-00678-3.
Tang, Jinyun, & Riley, William J. Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations. Netherlands. doi:https://doi.org/10.1007/s10533-020-00678-3
Tang, Jinyun, and Riley, William J. Thu . "Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations". Netherlands. doi:https://doi.org/10.1007/s10533-020-00678-3.
@article{osti_1630347,
title = {Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations},
author = {Tang, Jinyun and Riley, William J.},
abstractNote = {Terrestrial carbon (C)-climate feedbacks depend strongly on how soil organic matter (SOM) decomposition responds to temperature. This dependency is often represented in land models by the parameter Q10, which quantifies the relative increase of microbial soil respiration per 10 °C temperature increase. Many studies have conducted paired laboratory soil incubations and inferred “active” and “slow” pool Q10 values by fitting linear two-pool models to measured respiration time series. Using a recently published incubation study (Qin et al. in Sci Adv 5(7):eaau1218, 2019) as an example, here we first show that the very high parametric equifinality of the linear two-pool models may render such incubation-based Q10 estimates unreliable. In particular, we show that, accompanied by the uncertain initial active pool size, the slow pool Q10 can span a very wide range, including values as high as 100, although all parameter combinations are producing almost equally good model fit with respect to the observations. This result is robust whether or not interactions between the active and slow pools are considered (typically these interactions are not considered when interpreting incubation data, but are part of the predictive soil carbon models). This very large parametric equifinality in the context of interpreting incubation data is consistent with the poor temporal extrapolation capability of linear multi-pool models identified in recent studies. Next, using a microbe-explicit SOM model (RESOM), we show that the inferred two pools and their associated parameters (e.g., Q10) could be artificial constructs and are therefore unreliable concepts for integration into predictive models. We finally discuss uncertainties in applying linear two-pool (or more generally multiple-pool) models to estimate SOM decomposition parameters such as temperature sensitivities from laboratory incubations. We also propose new observations and model structures that could enable better process understanding and more robust predictive capabilities of soil carbon dynamics.},
doi = {10.1007/s10533-020-00678-3},
journal = {Biogeochemistry},
number = 3,
volume = 149,
place = {Netherlands},
year = {2020},
month = {5}
}

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DOI: https://doi.org/10.1007/s10533-020-00678-3

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