Soil Organic Carbon Stabilization: Mapping Carbon Speciation from Intact Microaggregates

The clearing of land for agricultural production depletes soil organic carbon (OC) reservoirs, yet despite their importance, the mechanisms by which C is stabilized in soils remain unclear. Using synchrotron-based infrared microspectroscopy, we have for the first time obtained in situ, laterally res...

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Published inEnvironmental science & technology Vol. 52; no. 21; pp. 12275 - 12284
Main Authors Hernandez-Soriano, Maria C, Dalal, Ram C, Warren, Frederick J, Wang, Peng, Green, Kathryn, Tobin, Mark J, Menzies, Neal W, Kopittke, Peter M
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 06.11.2018
Subjects
Aggregates
Agricultural land
Agricultural production
Aliphatic compounds
Carbon
Concentration gradient
Organic carbon
Organic soils
Polysaccharides
Soil mapping
Soil stabilization
Soils
Speciation
Stability
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Summary:The clearing of land for agricultural production depletes soil organic carbon (OC) reservoirs, yet despite their importance, the mechanisms by which C is stabilized in soils remain unclear. Using synchrotron-based infrared microspectroscopy, we have for the first time obtained in situ, laterally resolved data regarding the speciation of C within sections taken from intact free microaggregates from two contrasting soils (Vertisol and Oxisol, 0–20 cm depth) impacted upon by long-term (up to 79 y) agricultural production. There was no apparent gradient in the C concentration from the aggregate surface to the interior for any of the three forms of C examined (aliphatic C, aromatic C, and polysaccharide C). Rather, organo-mineral interactions were of critical importance in influencing overall C stability, particularly for aliphatic C, supporting the hypothesis that microaggregates form through organo-mineral interactions. However, long-term cropping substantially decreased the magnitude of the organo-mineral interactions for all three forms of C. Thus, although organo-mineral interactions are important for OC stability, C forms associated with the mineral phases are not entirely resistant to degradation. These results provide important insights into the underlying mechanisms by which microaggregates form and the factors influencing the persistence of OC in soils.
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ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.8b03095