Importance of microbial soil organic matter processing in dissolved organic 
carbon production

Malik, Ashish; Gleixner, Gerd

doi:10.1111/1574-6941.12182

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Importance of microbial soil organic matter processing in dissolved organic carbon production

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Malik, Ashish
Molecular Biogeochemistry Group, Dr. G. Gleixner, Department Biogeochemical Processes, Prof. S. E. Trumbore, Max Planck Institute for Biogeochemistry, Max Planck Society;
IMPRS International Max Planck Research School for Global Biogeochemical Cycles, Max Planck Institute for Biogeochemistry , Max Planck Society;

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Gleixner, Gerd
Molecular Biogeochemistry Group, Dr. G. Gleixner, Department Biogeochemical Processes, Prof. S. E. Trumbore, Max Planck Institute for Biogeochemistry, Max Planck Society;

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http://dx.doi.org/10.1111/1574-6941.12182
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Citation

Malik, A., & Gleixner, G. (2013). Importance of microbial soil organic matter processing in dissolved organic carbon production. FEMS Microbiology Ecology, 86(1), 139-148. doi:10.1111/1574-6941.12182.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0014-1B47-3

Abstract

Soil dissolved organic carbon (DOC) sources and its seasonal dynamics are poorly known. We aimed to determine the contribution of plant and soil organic matter (SOM) to size classes of DOC in a field experiment with C3 to C4 vegetation change on two soil types through different seasons. Stable isotope ratios of DOC size classes were measured using size-exclusion chromatography (SEC) coupled on-line to liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). SEC resolved DOC into three size classes: very high molecular weight/vHMW (>10 kDa), high molecular weight/HMW (0.4-10 kDa) and low molecular weight/LMW (< 0.4 kDa). HMW DOC was most abundant in all seasons, soil types and depths. In contrast, vHMW DOC was only seen post snowmelt in upper 20 cm and was mainly (87±9 %) plant-derived. Through all seasons, HMW and LMW DOC had less than 30% recent plant contribution. Similar size range and source of DOC size classes and soil chloroform fumigation extracts suggest microbial origin of DOC. Thus microbial SOM recycling is an important process in DOC production. We suggest that DOC molecules get partitioned manifold between soil solution and the mineral matrix (chromatography) thereby getting constantly decomposed, altered or produced anew by soil microorganisms (reactive transport).