Landscape patterns and soil organic carbon stocks in agricultural bocage landscapes

Soil organic carbon (SOC) has a crucial impact on global carbon storage at world scale. SOC spatial variability iscontrolled by the landscape patterns resulting from the continuous interactions between the physical environmentand the society. Natural and anthropogenic processes occurring and interplaying at the landscape scale, such as soilredistribution in the lateral and vertical dimensions by tillage and water erosion processes or spatial differentiationof land-use and land-management practices, strongly affect SOC dynamics. Inventories of SOC stocks, reflectingtheir spatial distribution, are thus key elements to develop relevant management strategies to improving carbonsequestration and mitigating climate change and soil degradation.This study aims to quantify SOC stocks and their spatial distribution in a 1,000-ha agricultural bocage landscapewith dairy production as dominant farming system (Zone Atelier Armorique, LTER Europe, NW France).The site is characterized by high heterogeneity on short distance due to a high diversity of soils with varyingwaterlogging, soil parent material, topography, land-use and hedgerow density. SOC content and stockswere measured up to 105-cm depth in 200 sampling locations selected using conditioned Latin hypercubesampling. Additive sampling was designed to specifically explore SOC distribution near to hedges: 112 pointswere sampled at fixed distance on 14 transects perpendicular from hedges. We illustrate the heterogeneityof spatial and vertical distribution of SOC stocks at landscape scale, and quantify SOC stocks in the variouslandscape components. Using multivariate statistics, we discuss the variability and co-variability of existingspatial organization of cropping systems, environmental factors, and SOM stocks, over landscape. Ultimately,our results may contribute to improving regional or national digital soil mapping approaches, by consideringthe distribution of SOC stocks within each modeling unit and by accounting for the impact of sensitive ecosystems.