The influence of catchment morphology, lithology and land use on soil organic carbon export in a Mediterranean mountain region

• Lithology and morphometric factors controlled total C export through soil erosion.
• Large forest cover was associated with higher C concentration in sediments but not higher C export.
• Morphometric factors were associated with higher variability of C concentration in sediments.

Soil erosion processes play an important role in the redistribution of soil organic carbon over the landscape. The factors controlling this carbon (C) redistribution have been thoroughly studied at the plot scale, but knowledge at the landscape level is still limited. In this study, we explore the role of different factors on C export at the catchment scale. We measured the C concentration in sediment deposited behind check-dams at the outlet of catchments ranging between 7 ha and 438 ha and combined it with specific sediment yield rates (SSY, Mg ha− 1 y− 1) to estimate catchment specific C yields (SCY, g m− 2 y− 1). Correlation analysis between C concentration, SCY and morphological, lithological and land use data derived from GIS analysis and interpretation of ortophotoimages was conducted. The results showed a close relationship between SCY rates and catchment morphometric properties such as catchment area, slope gradient and lithology, while C concentration in sediments was correlated to the percentage of forest cover in a catchment. In addition, it is suggested that morphological properties such as average slope gradient, drainage area and drainage density could have implications for the fate and stability of C stored at depositional sites through changes in the in-depth variability of C concentration in sediments and in the concentration of two measured C fractions. Further research is needed in this direction.