Publishable report on landscape characterisation focusing on the extent and suitability of CSL systems based on model output

Deliverable 7.4 builds upon the foundation established in Deliverable 7.1, which focused on characterising the landscape and mapping the suitability of Crop, Shrub, and Livestock (CSL) or agrosylvopastoral systems for the SustainSahel sites. This deliverable presents a detailed mapping of 25 agro-environmental variables, including precipitation, altitude, soil types, soil organic carbon, and tree and shrub cover. The analysis was conducted at both regional levels (Senegal, Mali, Burkina Faso) and specific sites (Saria, Yilou, Koulikoro, Sikasso, Niakhar, Ouarkhokh, Koussanar) using geospatial databases such as WaPOR, ISRIC, and TAMSAT. The primary goal of Deliverable 7.4 is to generate a suitability map for CSL systems across the three countries and model the yield benefits of these systems under varying isohyets within the studied landscapes using the LUCIA model. The suitability of CSL systems for the target areas was modelled using the Random Forest machine learning algorithm. The assessment of the agrosylvopastoral system's suitability incorporated agro-environmental variables obtained from freely accessible online platforms, vegetation indices derived from Landsat 8 satellite imagery, and field-collected occurrence data on agroforestry systems. All analyses were conducted using the Google Earth Engine platform. The LUCIA model (lucia.uni-hohenheim.de) was calibrated and validated for key crops, including millet and sorghum, as well as shrubs and trees across the SustainSahel study sites. Simulations were conducted to estimate crop yields and biomass production potential of shrubs and trees under different isohyets at each location. The effectiveness of various CSL systems in enhancing crop grain yield was assessed by comparing their benefits under different soil amendment treatments to baseline yields (no amendment). Additionally, aboveground biomass production of trees and shrubs and yields benefits of cereals intercropped with shrubs and trees were evaluated across different landscape positions with varying isohyets. The CSL suitability map indicates that western Senegal, central Mali, and northern Burkina Faso are the most favorable regions for agrosylvopastoralism, while northern Mali is significantly less suitable. The yield simulations conducted using the LUCIA model aligned with these suitability findings. In Senegal, higher yield benefits were observed in Niakhar (western region) compared to the northern area around Ouarkhokh and the southern zone near Koussanar. Similarly, in Mali, Koulikoro's central region showed greater yield benefits than Sikasso in the south. In Burkina Faso, Yilou in the north exhibited more pronounced yield gains than Saria in the south. The results also highlight that while higher yield benefits were generally associated with regions of higher isohyets, some areas displayed contrasting trends. This suggests that factors beyond rainfall, such as soil fertility, may also play a significant role. The integrated use of organic and mineral fertilizers was found to enhance yield benefits even in areas with lower isohyets. Aboveground biomass (AGB) production contributes to both animal nutrition and soil fertility through the incorporation of pruned residues. In regions with 500 shrubs ha-1, AGB exhibited minimal variability and remained stable across different isohyets in the three studied countries, in contrast to the 1000 shrubs per hectare density. At the higher planting density (1000 shrubs ha-1), AGB was generally greater in areas with lower isohyets than in those with higher isohyets, except in certain locations. Overall, AGB production increased with higher planting densities of Guiera senegalensis. Intercropping cereals with Guiera senegalensis improved yields across all study regions, with the most significant benefits observed in lower isohyets, particularly in Saria and Yilou, Burkina Faso. Similarly, intercropping Faidherbia albida with cereals resulted in higher yields benefits. However, in most study regions, the yield benefits of Faidherbia albida intercropping were more pronounced in areas with higher isohyets than in those with lower isohyets.