Quantifying charcoal degradation and negative priming of soil organic matter with a c-14-dead tracer

Tilston, Emma L., Ascough, Philippa L., Garnett, Mark H., and Bird, Michael I. (2016) Quantifying charcoal degradation and negative priming of soil organic matter with a c-14-dead tracer. Radiocarbon, 58 (4). pp. 905-919.

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Abstract

Converting biomass to charcoal produces physical and chemical changes greatly increasing environmental recalcitrance, leading to great interest in the potential of this carbon form as a long-term sequestration strategy for climate change mitigation. Uncertainty remains, however, over the timescale of charcoal's environmental stability, with estimates varying from decadal to millennial scales. Uncertainty also remains over charcoal's effect on other aspects of carbon biogeochemical cycling and allied nutrient cycles such as nitrogen. Radiocarbon is a powerful tool to investigate charcoal mineralization due to its sensitivity; here we report the results of a study using C-14-dead charcoal (pMC = 0.137 +/- 0.002) in organic-rich soil (pMC = 99.76 +/- 0.46), assessing charcoal degradation over 55 days of incubation. Using this method, we discriminated between decomposition of indigenous soil organic matter (SOM) and charcoal by microorganisms. SOM was the major source of carbon respired from the soil, but there was also a contribution from charcoal carbon mineralization. This contribution was 2.1 and 1.1% on days 27 and 55, respectively. We also observed a negative priming effect due to charcoal additions to soil, where SOM mineralization was repressed by up to 14.1%, presumably arising from physico-chemical interactions between soil and charcoal.

Item ID: 47042
Item Type: Article (Research - C1)
ISSN: 0033-8222
Keywords: biochar, black carbon, charcoal, molecular sieve, soil respiration
Funders: National Environmental Research Council (NERC)
Projects and Grants: NERC NRCF010001 (alloc. 1510.1010) & NE/F017456/1
Date Deposited: 11 Jan 2017 07:36
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 50%
05 ENVIRONMENTAL SCIENCES > 0503 Soil Sciences > 050301 Carbon Sequestration Science @ 50%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960302 Climate Change Mitigation Strategies @ 25%
96 ENVIRONMENT > 9609 Land and Water Management > 960904 Farmland, Arable Cropland and Permanent Cropland Land Management @ 25%
97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 50%
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