Understanding large-extent controls of soil organic carbon storage in relation to soil depth and soil-landscape systems

• Published in: Global biogeochemical cycles 2015-08, Vol.29 (8), p.1210-1229
• Main Authors: Mulder, Vera L., Lacoste, Marine, Martin, Manuel P., Richer-de-Forges, Anne, Arrouays, Dominique
• Format: Article
• Language: English
• Subjects: Carbon sequestration; Climatic conditions; Data mining; Environmental Sciences; Global Changes; Herbivores; model-based clustering; Organic carbon; Organic matter; Soil depth; soil organic carbon; Soil texture; soil-landscape systems; spatial variation; Subsoils; Topsoil; Water availability; Water depth
• ISSN: 0886-6236; 1944-9224; 1944-8224
• DOI: 10.1002/2015GB005178

In this work we aimed at developing a conceptual framework in which we improve our understanding of the controlling factors for soil organic carbon (SOC) over vast areas at different depths. We postulated that variability in SOC levels may be better explained by modeling SOC within soil‐landscape systems (SLSs). The study was performed in mainland France, and explanatory SOC models were developed for the sampled topsoil (0–30 cm) and subsoil (>30 cm), using both directed and undirected data‐mining techniques. With this study we demonstrated that there is a shift in controlling factors both in space and depth which were mainly related to (1) typical SLS characteristics and (2) human‐induced changes to SLSs. The controlling factors in relation to depth alter from predominantly biotic to more abiotic with increasing depth. Especially, water availability, soil texture, and physical protection control deeper stored SOC. In SLSs with similar SOC levels, different combinations of physical protection, the input of organic matter, and climatic conditions largely determined the SOC level. The SLS approach provided the means to partition the data into data sets that were having homogenous conditions with respect to this combination of controlling factors. This information may provide important information on the carbon storage and sequestration potential of a soil. Key Points SOC drivers alter from mainly biotic to abiotic with increasing soil depth SOC storage depends on physical protection in addition to climate and OC input Soil‐landscape systems explain large‐extent SOC dynamics in space and depth