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Volume 4, issue 2 | Copyright
SOIL, 4, 153-167, 2018
https://doi.org/10.5194/soil-4-153-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Original research article 06 Jun 2018

Original research article | 06 Jun 2018

Hot regions of labile and stable soil organic carbon in Germany – Spatial variability and driving factors

Cora Vos, Angélica Jaconi, Anna Jacobs, and Axel Don Cora Vos et al.
  • Thünen Institute of Climate-Smart Agriculture, Bundesallee 65, 38116 Braunschweig, Germany

Abstract. Atmospheric carbon dioxide levels can be mitigated by sequestering carbon in the soil. Sequestration can be facilitated by agricultural management, but its influence is not the same on all soil carbon pools, as labile pools with a high turnover may be accumulated much faster but are also more vulnerable to losses. The aims of this study were to (1) assess how soil organic carbon (SOC) is distributed among SOC fractions on a national scale in Germany, (2) identify factors influencing this distribution and (3) identify regions with high vulnerability to SOC losses. The SOC content and proportion of two different SOC fractions were estimated for more than 2500 mineral topsoils (<87gkg−1 SOC) covering Germany, using near-infrared reflectance spectroscopy. Drivers of the spatial variability in SOC fractions were determined using the machine learning algorithm cforest. The SOC content and proportions of fractions were predicted with good accuracy (SOC content: R2 = 0.87–0.90; SOC proportions: R2 = 0.83; ratio of performance to deviation (RPD): 2.4–3.2). The main explanatory variables for the distribution of SOC among the fractions were soil texture, bulk soil CN ratio, total SOC content and pH. For some regions, the drivers were linked to the land-use history of the sites.

Arable topsoils in central and southern Germany were found to contain the highest proportions and contents of stable SOC fractions, and therefore have the lowest vulnerability to SOC losses. North-western Germany contains an area of sandy soils with unusually high SOC contents and high proportions of light SOC fractions, which are commonly regarded as representing a labile carbon pool. This is true for the former peat soils in this area, which have already lost and are at high risk of losing high proportions of their SOC stocks. Those black sands can, however, also contain high amounts of stable SOC due to former heathland vegetation and need to be treated and discussed separately from non-black sand agricultural soils. Overall, it was estimated that, in large areas all over Germany, over 30% of SOC is stored in easily mineralisable forms. Thus, SOC-conserving management of arable soils in these regions is of great importance.

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Soil organic carbon sequestration can be facilitated by agricultural management, but its influence is not the same on all soil carbon pools. We assessed how soil organic carbon is distributed among C pools in Germany, identified factors influencing this distribution and identified regions with high vulnerability to C losses. Explanatory variables were soil texture, C / N ratio, soil C content and pH. For some regions, the drivers were linked to the land-use history as heathlands or peatlands.
Soil organic carbon sequestration can be facilitated by agricultural management, but its...
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