Regional SOC inventory in the Belgian loam belt

Stevens, François [UCL] Bogaert, Patrick [UCL] van Wesemael, Bas [UCL]

The global carbon cycle has an important influence on global change. Soil organic carbon (SOC) is the largest component of the terrestrial carbon pooland plays a vital role in the terrestrial carbon cycle. However, it remains a challenge to accurately quantify SOC stocks and evolution at regional scale. The general objective of the research is to improve the regional SOC inventories and scenarios by taking into account the lateral fluxes of sediments and carbon. The study focuses on the cultivated areas of the Belgian loam belt. The first part of the project consists in constructing a 3-dimensional SOC map of a study area inside the loam belt, from soil profile description and ancillary environmental data. The digital soil database Aardewerk provided georeferenced soil profile description across all the Belgian loam belt. A Monte Carlo method was used to account for the uncertainty in the horizons boundaries. Different methods permitting to construct continuous distribution of SOC density from bulk horizon measurements were compared. Colluvial properties were searched in the profile description database that best characterized the erosion-accumulation pattern of the region. Different topographic indices were computed from digital elevation models to assess the influence of the topography on the SOC distribution. A linear regression analysis was conducted in order to predict the SOC spatial distribution at different depth intervals from soil and terrain properties. Using the resulting model, maps of SOC and other soil properties at differents depths, and representative of the situation in ~1960, will be constructed. These maps will be next used as input data for processed-based model coupling lateral fluxes of sediment and carbon turnover.