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Temperature response of permafrost soil carbon is attenuated by mineral protection
Author(s) -
Gentsch Norman,
Wild Birgit,
Mikutta Robert,
Čapek Petr,
Diáková Katka,
Schrumpf Marion,
Turner Stephanie,
Minnich Cynthia,
Schaarschmidt Frank,
Shibistova Olga,
Schnecker Jörg,
Urich Tim,
Gittel Antje,
Šantrůčková Hana,
Bárta Jiři,
Lashchinskiy Nikolay,
Fuß Roland,
Richter Andreas,
Guggenberger Georg
Publication year - 2018
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.14316
Subject(s) - permafrost , soil water , environmental chemistry , soil carbon , mineralization (soil science) , subsoil , total organic carbon , organic matter , soil organic matter , q10 , fractionation , arctic , soil science , chemistry , environmental science , geology , respiration , botany , oceanography , organic chemistry , biology
Climate change in Arctic ecosystems fosters permafrost thaw and makes massive amounts of ancient soil organic carbon ( OC ) available to microbial breakdown. However, fractions of the organic matter ( OM ) may be protected from rapid decomposition by their association with minerals. Little is known about the effects of mineral‐organic associations ( MOA ) on the microbial accessibility of OM in permafrost soils and it is not clear which factors control its temperature sensitivity. In order to investigate if and how permafrost soil OC turnover is affected by mineral controls, the heavy fraction ( HF ) representing mostly MOA was obtained by density fractionation from 27 permafrost soil profiles of the Siberian Arctic. In parallel laboratory incubations, the unfractionated soils (bulk) and their HF were comparatively incubated for 175 days at 5 and 15°C. The HF was equivalent to 70 ± 9% of the bulk CO 2 respiration as compared to a share of 63 ± 1% of bulk OC that was stored in the HF . Significant reduction of OC mineralization was found in all treatments with increasing OC content of the HF ( HF ‐ OC ), clay‐size minerals and Fe or Al oxyhydroxides. Temperature sensitivity (Q10) decreased with increasing soil depth from 2.4 to 1.4 in the bulk soil and from 2.9 to 1.5 in the HF . A concurrent increase in the metal‐to‐ HF ‐ OC ratios with soil depth suggests a stronger bonding of OM to minerals in the subsoil. There, the younger 14 C signature in CO 2 than that of the OC indicates a preferential decomposition of the more recent OM and the existence of a MOA fraction with limited access of OM to decomposers. These results indicate strong mineral controls on the decomposability of OM after permafrost thaw and on its temperature sensitivity. Thus, we here provide evidence that OM temperature sensitivity can be attenuated by MOA in permafrost soils.