TY - JOUR

T1 - Temperature response of permafrost soil carbon is attenuated by mineral protection

AU - Gentsch, Norman

AU - Wild, Birgit

AU - Mikutta, Robert

AU - Čapek, Petr

AU - Diáková, Katka

AU - Schrumpf, Marion

AU - Turner, Stephanie

AU - Minnich, Cynthia

AU - Schaarschmidt, Frank

AU - Shibistova, Olga

AU - Schnecker, Jörg

AU - Urich, Tim

AU - Gittel, Antje

AU - Šantrůčková, Hana

AU - Bárta, Jiři

AU - Lashchinskiy, Nikolay

AU - Fuß, Roland

AU - Richter, Andreas

AU - Guggenberger, Georg

N1 - © 2018 John Wiley & Sons Ltd

PY - 2018/7/3

Y1 - 2018/7/3

N2 - 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 CO2 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 14C signature in CO2 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.

AB - 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 CO2 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 14C signature in CO2 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.

KW - carbon mineralization

KW - incubation

KW - mineral-organic association

KW - permafrost soils

KW - radiocarbon

KW - temperature sensitivity

UR - http://www.scopus.com/inward/record.url?scp=85047829376&partnerID=8YFLogxK

U2 - 10.1111/gcb.14316

DO - 10.1111/gcb.14316

M3 - Article

C2 - 29774972

AN - SCOPUS:85047829376

VL - 24

SP - 3401

EP - 3415

JO - Global change biology

JF - Global change biology

SN - 1354-1013

IS - 8

ER -