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Relationships between Biological and Thermal Indices of Soil Organic Matter Stability Differ with Soil Organic Carbon Level
Author(s) -
Peltre Clément,
Fernández José M.,
Craine Joseph M.,
Plante Alain F.
Publication year - 2013
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2013.02.0081
Subject(s) - soil water , organic matter , thermal stability , soil organic matter , environmental chemistry , chemistry , differential scanning calorimetry , soil test , soil carbon , thermogravimetry , soil science , mineralogy , environmental science , inorganic chemistry , physics , organic chemistry , thermodynamics
Thermal analysis techniques can provide an important addition to our understanding of soil organic matter (SOM) composition and stability. Several recent studies have linked thermal and biological stability of SOM; however, contrasting results have been reported. The objective of this study was to characterize the relationships between thermal and biological SOM stability for a wide range of mineral soils. Soils were collected from 28 sites from across the United States and analyzed by thermogravimetry (TG) and differential scanning calorimetry (DSC) coupled with CO 2 evolved gas analysis (CO 2 –EGA). We compared thermal analysis results to mean soil respiration rates during incubation at 20°C for 365 d (R 20 ). For soils with <30 g C kg −1 (low C), R 20 was negatively correlated with the temperature at which half of the DSC energy is released and the temperature at which half of the CO 2 –EGA is evolved. Conversely, for soils with >30 g C kg −1 (high C), R 20 was positively correlated with CO 2 –EGA and DSC energy released between 345 and 460°C and to SOM energy density (in J mg −1 C). Differences between low‐C and high‐C soils indicate the relative importance of mineral association of SOM in low‐C soils and the abundance of intact plant debris that is relatively energy dense and thermally resistant but relatively easy to decompose in high‐C soils. Above all, thermal analysis proved to be a useful technique for interpreting SOM stability, but sample C concentration must be considered because it affects the dominant SOM stabilization mechanisms and thermal analysis results.