Tree density and biomass assessment in agricultural systems around Lake Victoria, Uganda

Abstract

Soil erosion caused by low vegetation cover associated with agricultural land use in the catchment is blamed for the eutrophication of Lake Victoria. Above-ground biomass as an indicator of vegetation cover and biodiversity was assessed using the Normalized Difference Vegetation Index, estimation of tree density and biomass with the aim of assessing the extent to which vegetation covers the soil surface. Tree density is significantly different between agricultural and semi-natural systems with an average of 96 and 90 trees ha)1 observed in Rakai and Mayuge respectively. Agricultural fields in Mayuge (9.4 ton ha)1) are associated with significantly higher tree biomass compared with those in Rakai (7.6 ton ha)1). Semi-natural systems in Rakai have an average tree biomass of 10.1 ton ha)1. Agricultural land use systems in the Lake Victoria catchment of Mayuge resemble semi-natural systems in terms of tree biomass as seen from satellite image analysis, supported by extensive field observations. The high and medium biomass cover does imply a relatively continuous vegetative ground cover that would minimize soil loss due to water erosion.