Using soil properties to indicate regulating ecosystem services in a Sudano-Sahelian agro-ecological landscape

Abstract: In semi-arid low yielding agro-ecological landscapes such as the Sahel both water and soil nutrients are limiting factors for crop growth. In addition to this there is a distinct difference in how well different land cover/land use types, so called ecotopes, perform in producing ecosystem services (ES) related to small-scale agriculture. This thesis seeks to explain differences in provisioning ES supply with the prevalence of regulating ES using indicators as proxies. The results show that the produced biomass is three times higher in the ecotope characterized as Depression than in Field. However, there are no or little significant differences between ecotopes regarding nutrients, organic matter and texture. In evaporation measurements the ecotope characterized as Fallow turned out to have the lowest evaporation rate, while there seemed to be little or no difference between Field and Depression. Water holding capacity, on the other hand, was slightly higher in Depression, which would mean that crops would manage a dry spell for between 6 to 10 days longer compared to other ecotopes. The absence of distinct differences in chemical and physical properties of the soil, even though this difference is evident in provisioning ES supply, shows that selecting relevant indicators is not easily done with available standard soil-plant systems indicators. Potential differences relating to water regulation could be further investigated by looking at factors that determine the direction of water flows and distance to ground water as a potential water supply for crops, e.g. topography, soil depth and the occurrence of crusts and hardpans as well as how they impact the patterns of runoff and runon in the landscape.