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Title: Isotope partitioning of soil respiration: A Bayesian solution to accommodate multiple sources of variability

Journal Article · · Journal of Geophysical Research. Biogeosciences
DOI:https://doi.org/10.1002/2014JG002794· OSTI ID:1454917
 [1];  [2]
  1. Arizona State Univ., Tempe, AZ (United States). School of Life Sciences
  2. Univ. of Western Sydney, NSW (Australia). Hawkesbury Inst. for the Environment; Univ. of Wyoming, Laramie, WY (United States). Dept. of Botany. Program in Ecology

Isotopic methods offer great potential for partitioning trace gas fluxes such as soil respiration into their different source contributions. Traditional partitioning methods face challenges due to variability introduced by different measurement methods, fractionation effects, and end-member uncertainty. To address these challenges, we describe in this paper a hierarchical Bayesian (HB) approach for isotopic partitioning of soil respiration that directly accommodates such variability. We apply our HB method to data from an experiment conducted in a shortgrass steppe ecosystem, where decomposition was previously shown to be stimulated by elevated CO2. Our approach simultaneously fits Keeling plot (KP) models to observations of soil or soil-respired δ13C and [CO2] obtained via chambers and gas wells, corrects the KP intercepts for apparent fractionation (Δ) due to isotope-specific diffusion rates and/or method artifacts, estimates method- and treatment-specific values for Δ, propagates end-member uncertainty, and calculates proportional contributions from two distinct respiration sources (“old” and “new” carbon). The chamber KP intercepts were estimated with greater confidence than the well intercepts and compared to the theoretical value of 4.4‰, our results suggest that Δ varies between 2 and 5.2‰ depending on method (chambers versus wells) and CO2 treatment. Because elevated CO2 plots were fumigated with 13C-depleted CO2, the source contributions were tightly constrained, and new C accounted for 64% (range = 55–73%) of soil respiration. The contributions were less constrained for the ambient CO2 treatments, but new C accounted for significantly less (47%, range = 15–82%) of soil respiration. Finally, our new HB partitioning approach contrasts our original analysis (higher contribution of old C under elevated CO2) because it uses additional data sources, accounts for end-member bias, and estimates apparent fractionation effects.

Research Organization:
Univ. of Wyoming, Laramie, WY (United States); Arizona State Univ., Tempe, AZ (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER); USDA Cooperative State Research, Education, and Extension Service (CSREES); National Science Foundation (NSF)
Grant/Contract Number:
SC0006973; 2008-35107-18655; DEB1021559
OSTI ID:
1454917
Alternate ID(s):
OSTI ID: 1402370
Journal Information:
Journal of Geophysical Research. Biogeosciences, Vol. 120, Issue 2; ISSN 2169-8953
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 18 works
Citation information provided by
Web of Science

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Cited By (3)

Monitoring CO2 emissions to gain a dynamic view of carbon allocation to arbuscular mycorrhizal fungi journal August 2016
The value of soil respiration measurements for interpreting and modeling terrestrial carbon cycling journal November 2016
Modeling soil CO 2 production and transport with dynamic source and diffusion terms: testing the steady-state assumption using DETECT v1.0 journal January 2018