Assessing the effects of land use change on soil physical properties and hydrological processes in the sub-humid tropical environment of West Africa

摘要

Land use is a key parameter in the hydrologic cycle. Tropical Africa is affected by intense land use change since decades, particularly deforestation and conversion to agricultural land. The aim of this study is to analyse the effects of land use change on the hydrologic processes and soil physical properties in a small catchment (Aguima catchment) in central Benin. Results from ped-ological, pedobiological and hydrological investigations within the Aguima catchment were taken into account. The effects of land use change on hydrologic processes were analysed by comparing two sub-catchments of the Aguima catchment with different land use (savannah/forest and agricultural land use). The study is part of the GLOWA IMPETUS project, which examines the effects of global change on the water cycle and water availability on a regional scale in Morocco and Benin. The investigations of this study revealed that due to reduced activity of the macrofauna the infiltration capacity is significantly lower in cultivated soils than in savannah and forest. This causes higher surface runoff and soil loss rates, which was also determined on erosion plots. The increased soil loss on fields has effects on soil physical properties like increase of gravel content and reduction of field capacity. The impact of reduced vegetation cover on the soil water dynamics was examined with soil moisture measurements on different land use. Due to higher evapotranspiration and water withdrawal the soil water content on forest and savannah plots was lower than on agricultural fields. The difference in the water yield of the forested and cultivated catchments was over 120 mm in the dry year 2001 and about 70 mm in the wetter year 2002.