Co-283 Spatial Distribution of Soil Organic Carbon Stock in Tunisia

This study aims to understand the spatial distribution of organic carbon and its sequestration potential in Tunisian soils. Soil organic carbon (SOC) stock was estimated in the 0-30 cm and to 0-100 cm soil depth for Tunisia using maps of soils and of the departments, combined with results from a soil database. The original soil classification was simplified to nine soils. Tunisia contains 24 governorates and 262 delegations. The entire soil database totalised 1576 soil profiles corresponding to 5024 soil horizons, the soil-governorate map association comprised 23160 map units (MU) and the soil-delegation map association included 41759 MU. The method used for estimation of SOC stocks is based on soils and departments maps combined with the results from soil database. The way of calculating SOC stocks for a given depth consisted in summing SOC stocks by layer determined as a product of bulk density, organic carbon concentration and layer thickness. We estimated the organic carbon stock profile by profile. Therefore, we used three methods for evaluating SOC stocks; by soil orders, governorate and by delegation. Bulk density values were calculated from pedotransfer functions when we had missing values. We calculated SOC stocks by classical methods by summing available values down to 1 meter. In total, Tunisian SOC stock was ranged between 1.031 and 1.131 Pg C in the 0 to 100 cm soil depth. However, in the upper layer (30 cm), soil carbon ranged between 0.417 and 0.455 Pg C.