Partitioning of microbially respired CO₂ between indigenous and exogenous carbon sources during biochar degradation using radiocarbon and stable carbon isotopes

Munksgaard, Niels C., McBeath, Anna V., Ascough, Philippa L., Levchenko, Vladimir A., Williams, Alan, and Bird, Michael I (2019) Partitioning of microbially respired CO₂ between indigenous and exogenous carbon sources during biochar degradation using radiocarbon and stable carbon isotopes. Radiocarbon, 61 (2). pp. 573-586.

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Abstract

Pyrolized carbon in biochar can sequester atmospheric CO₂ into soil to reduce impacts of anthropogenic CO₂ emissions. When estimating the stability of biochar, degradation of biochar carbon, mobility of degradation products, and ingress of carbon from other sources must all be considered. In a previous study we tracked degradation in biochars produced from radiocarbon-free wood and subjected to different physico-chemical treatments over three years in a rainforest soil. Following completion of the field trial, we report here a series of in-vitro incubations of the degraded biochars to determine CO₂ efflux rates, ¹⁴C concentration and δ¹³C values in CO₂ to quantify the contributions of biochar carbon and other sources of carbon to the CO₂ efflux. The ¹⁴C concentration in CO₂ showed that microbial degradation led to respiration of CO₂ sourced from indigenous biochar carbon (approximate to 0.5-1.4 μmoles CO₂/g biochar C/day) along with a component of carbon closely associated with the biochars but derived from the local environment. Correlations between ¹⁴C concentration, δ¹³C values and Ca abundance indicated that Ca²⁺ availability was an important determinant of the loss of biochar carbon.

Item ID: 57905
Item Type: Article (Research - C1)
ISSN: 1945-5755
Keywords: ¹³C, ¹⁴C, biochar, degradation, immobilization, respiration
Copyright Information: © 2018 by the Arizona Board of Regents on behalf of the University of Arizona.
Funders: Australian Research Council (ARC), Australian Nuclear Science and Technology Organisation (ANSTO)
Projects and Grants: ARC Laureate Fellowship FL140100044, ANSTO Portal grant PE10105
Date Deposited: 10 Apr 2019 07:35
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0503 Soil Sciences > 050301 Carbon Sequestration Science @ 100%
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