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© Thünen-Institut/AK
[Translate to English:]
Institute of

AK Climate-Smart Agriculture



[Translate to English:]
© Thünen-Institut/AK
[Translate to English:]

SUBSOM - The Forgotten Part of Carbon Cycling: Organic Matter Storage and Turnover in Subsoils

Soils contain the largest carbon (C) pool of the global terrestrial C cycle. More than 50% of the C stocks are stored in deeper soil horizons. The processes of C stabilization in soils and how they are affected by anthropogenic activities are current research topics.

Background and Objective

The collaborative research project SUBSOM (DFG-research group), which combines nine sub-projects, investigates the key issues of the C-dynamics in subsoils. This will give a better understanding of the factors controlling C turnover and fluxes in the subsoil. Due to very low C concentrations and high spatial variability of soil properties and processes, the investigations in the subsoil pose major methodological, instrumental and analytical challenges. The SUBSOM project will face these challenges applying innovative approaches such as the use of combined stable and radiocarbon isotope analysis. Within the framework of the SUBSOM project, the Thünen Institute of Climate-Smart Agriculture investigates the CO2 production and the factors influencing the turnover of C in subsoils. The main objectives are:

  1. determination of CO2 production and subsoil C mineralization in situ
  2. investigation of the vertical distribution and origin of CO2 in the soil profile using soil air and isotope analysis
  3. evaluation of the environmental controls on subsoil C turnover in lab experiments


The study site was established in summer 2013 and it is located in a deciduous forest near to Hannover. On the site three accessible soil observatories were installed in 2 m depth. In each soil observatory CO2-concentration will be measured continuously in five different depths. In addition, gas samples will be taken at the same depths several times a year and these samples will be analysed on radiocarbon and stable C isotopes. In order to get information of vertical dynamics of C in soils 13C-labeled leaf litter will be exposed one on half at all three soil observatories in autumn 2014.

Additionally, laboratory incubation experiments will be carried out in order to investigate the key factors for C turnover in subsoils.


Scientific publication:

Wordell-Dietrich P, Don A, Helfrich M (2016) Controlling factors for the stability of subsoil carbon in a dystric cambisol. Geoderma:in press, DOI:10.1016/j.geoderma.2016.08.023

Involved external Thünen-Partners

Funding Body

  • Deutsche Forschungsgemeinschaft (DFG)
    (national, öffentlich)


5.2013 - 12.2020

More Information

Project funding number: HE 6877/1-1 und DO-1734/4-2
Project status: finished


  1. 0

    Kalks F, Liebmann P, Wordell-Dietrich P, Guggenberger G, Kalbitz K, Mikutta R, Helfrich M, Don A (2020) Fate and stability of dissolved organic carbon in topsoils and subsoils under beech forests. Biogeochemistry 148:111-128, DOI:10.1007/s10533-020-00649-8

  2. 1

    Wotte A, Wordell-Dietrich P, Wacker L, Don A, Rethemeyer J (2017) 14CO2 processing using an improved and robust molecular sieve cartridge. Nuclear Instruments Methods Phys Res B400:65-73

  3. 2

    Wordell-Dietrich P, Don A, Helfrich M (2017) Controlling factors for the stability of subsoil carbon in a dystric cambisol. Geoderma 304:40-48, DOI:10.1016/j.geoderma.2016.08.023

  4. 3

    Heinze S, Ludwig B, Piepho HP, Mikutta R, Don A, Wordell-Dietrich P, Helfrich M, Hertel D, Leuschner C, Kirfel K, Kandeler E, Preusser S, Guggenberger G, Leinemann T, Marschner B (2017) Factors controlling the variability of organic matter in the top- and subsoil of a sandy Dystric Cambisol under beech forest. Geoderma 311:37-44, DOI:10.1016/j.geoderma.2017.09.028

  5. 4

    Schiedung M, Don A, Wordell-Dietrich P, Alcantara V, Kuner P, Guggenberger G (2017) Thermal oxidation does not fractionate soil organic carbon with differing biological stabilities. J Plant Nutr Soil Sci 180:18-26, DOI:10.1002/jpln.201600172

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