TY - JOUR

T1 - Fate and stability of dissolved organic carbon in topsoils and subsoils under beech forests

AU - Kalks, Fabian

AU - Liebmann, Patrick

AU - Wordell-Dietrich, Patrick

AU - Guggenberger, Georg

AU - Kalbitz, Karsten

AU - Mikutta, Robert

AU - Helfrich, Mirjam

AU - Don, Axel

N1 - Funding information: Open Access funding provided by Projekt DEAL. This study was funded by the Deutsche Forschungsgemeinschaft (DFG) (DO1734/4–2) within the framework of the research unit SUBSOM (FOR1806)—“The Forgotten Part of Carbon Cycling: Organic Matter Storage and Turnover in Subsoils”. We would like to thank Frank Hegewald and the student assistants for their support in the field and in the laboratory, Roland Fuß for his detailed help regarding the application of a generalised linear mixed effect model and Jens Dyckmanns and Lars Szwec from the Centre for Stable Isotope Research and Analysis at the University of Göttingen for 13 CO 2 measurements. We would also like to thank the AK laboratory team for their support and patience with a disorder inducing experiment.

PY - 2020/3

Y1 - 2020/3

N2 - Dissolved organic carbon (DOC) from Oa horizons has been proposed to be an important contributor for subsoil organic carbon stocks. We investigated the fate of DOC by directly injecting a DOC solution from 13C labelled litter into three soil depths at beech forest sites. Fate of injected DOC was quantified with deep drilling soil cores down to 2 m depth, 3 and 17 months after the injection. 27 ± 26% of the injected DOC was retained after 3 months and 17 ± 22% after 17 months. Retained DOC was to 70% found in the first 10 cm below the injection depth and on average higher in the topsoil than in the subsoil. After 17 months DOC in the topsoil was largely lost (− 19%) while DOC in the subsoil did not change much (− 4.4%). Data indicated a high stabilisation of injected DOC in the subsoils with no differences between the sites. Potential mineralisation as revealed by incubation experiments however, was not different between DOC injected in topsoil or subsoils underlining the importance of environmental factors in the subsoil for DOC stabilisation compared to topsoil. We conclude that stability of DOC in subsoil is primary driven by its spatial inaccessibility for microorganisms after matrix flow while site specific properties did not significantly affect stabilisation. Instead, a more fine-textured site promotes the vertical transport of DOC due to a higher abundance of preferential flow paths.

AB - Dissolved organic carbon (DOC) from Oa horizons has been proposed to be an important contributor for subsoil organic carbon stocks. We investigated the fate of DOC by directly injecting a DOC solution from 13C labelled litter into three soil depths at beech forest sites. Fate of injected DOC was quantified with deep drilling soil cores down to 2 m depth, 3 and 17 months after the injection. 27 ± 26% of the injected DOC was retained after 3 months and 17 ± 22% after 17 months. Retained DOC was to 70% found in the first 10 cm below the injection depth and on average higher in the topsoil than in the subsoil. After 17 months DOC in the topsoil was largely lost (− 19%) while DOC in the subsoil did not change much (− 4.4%). Data indicated a high stabilisation of injected DOC in the subsoils with no differences between the sites. Potential mineralisation as revealed by incubation experiments however, was not different between DOC injected in topsoil or subsoils underlining the importance of environmental factors in the subsoil for DOC stabilisation compared to topsoil. We conclude that stability of DOC in subsoil is primary driven by its spatial inaccessibility for microorganisms after matrix flow while site specific properties did not significantly affect stabilisation. Instead, a more fine-textured site promotes the vertical transport of DOC due to a higher abundance of preferential flow paths.

KW - 13C

KW - Cascade model

KW - Field experiment

KW - Forest subsoils

KW - Incubation experiment

UR - http://www.scopus.com/inward/record.url?scp=85081201718&partnerID=8YFLogxK

U2 - 10.1007/s10533-020-00649-8

DO - 10.1007/s10533-020-00649-8

M3 - Article

AN - SCOPUS:85081201718

VL - 148

SP - 111

EP - 128

JO - BIOGEOCHEMISTRY

JF - BIOGEOCHEMISTRY

SN - 0168-2563

IS - 2

ER -