Yazidhi Bamutaze

A field assessment of land use systems and soil properties at varied landscape positions in a fragile ecosystem of Mount Elgon, Uganda

The purpose of this field study was to identify and characterize land use systems at varied spatial hierarchies, and to differentiate soil properties along varied landscape positions. Key data about existing land use systems and soil properties were systematically collected in 12 sites. Topographic profiles across catchment and geomorphic units were identified to show the relation typical of a mountain ecosystem. We found statistically significant differences (p < .05) in soil properties along altitudinal gradients in 52% of the samples and also in land use and land cover distribution characteristics along the slope gradients. The most dominant soils were sandy loam on the hillslopes and clay loams at the footslopes; and most of the cultivated fields were located on slopes ranging from 0 to 17%. The livestock production system was based on a small constructed unit with a capacity to enable feed resources. Soil conservation practices that were evident among the study sites included the use of mulching, hedgerows, intercropping, fallowing, and minimum tillage. Deep empirical knowledge of this system will further advance our understanding on how a fragile ecosystem responds to both natural and human-caused change, and its associated impact on the surrounding environment.

Climate change and land degradation in Africa: a case study in the Mount Elgon region, Uganda

The aim of this study is to estimate and compare soil erosion, in the Mount Elgon region, eastern Uganda, during the last decade. Possible trends and changes in erosion are linked to precipitation/climate change as well as changes in land cover. Two different versions of the Revised Universal Soil loss Equation (RUSLE) are implemented and compared, one using slope length and the other using flow accumulation to estimate the slope length and steepness factor (LS). Comparisons of the modeled soil erosion vs. field data indicate that RUSLE based on flow accumulation is preferable. The modeling is carried out for the years 2000, 2006, and 2012, and is based on ASTER remotely sensed data, digital elevation models, precipitation data from the study area, as well as existing soil maps. No significant trends in estimated soil erosion are found to be present during the last decade. Over exploitation of land is probably compensated by improved agricultural management and no significant increase in precipitation. Even if there are reports of more intense and increasing amounts of rainfall in the area, this could not be verified, neither through the analysis of climate data, nor by trends in the estimated soil loss.

Geopedological and Landscape Dynamic Controls on Productivity Potentials and Constraints in Selected Spatial Entities in Sub-Saharan Africa

Soil-landscape relations play an important role in the agricultural production systems of Sub-Saharan Africa. As the demands on elevated agricultural productivity grows in the face of increasing demographic pressure and the adverse impacts of global environmental change, we must identify socio-ecological production landscapes that are resilient to environmental changes. This paper analyses a spectrum of spatial and non-spatial datasets covering soil, terrain, land use, and geology in a GIS environment to derive spatial entities that inform the production potentials and constraints of East Africa. Landscape analysis, premised on the geopedological and elevation constructs, culminated in a spatial coverage of lowlands (40 %), plateaux (46 %), highlands (11 %) and mountains (3 %) across the East African region. Regional-level analysis reveals spatially variable soil typologies dominated by Cambisols (24 %) and Ferralsols (13 %). In these geomorphic landscapes and soil types, there are two outstanding anthropogenic threats to productivity: soil erosion and land use/cover conversions and transformations. These must be delicately tackled with site-specific tailored interventions that not only recognize geopedological landscape sensitivity, but also the inherent social systems.

Determining hydrological regimes in an agriculturally used tropical inland valley wetland in Central Uganda using soil moisture, groundwater, and digital elevation data

Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany Steinmann Institute of Geology, Palaeontology, and Mineralogy, University of Bonn, Nussallee 8, 53115 Bonn, Germany Department of Geomatics and Land Management, Makerere University, P.O. Box 7062, Kampala, Uganda Department of Geography, Geoinformatics, and Climatic Sciences, Makerere University, P. O. Box 7062, Kampala, Uganda Correspondence Geofrey Gabiri, Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany. Email: geofreygabiri@gmail.com

Assessing the Performance of WRF Model in Simulating Rainfall over Western Uganda

Skillful rainfall prediction is important to sectors such as agriculture, health and water resources. The study assessed the ability of the Weather Research and Forecasting model to simulate rainfall over Western Uganda for the period 21st April to 10th May 2013 and tested six cumulus parameterization schemes. The root mean square error, mean error and the sign test method are used to assess the ability of the schemes to simulate rainfall along with an adapted contingency table. Results show that the Grell-Fretas scheme is better at simulating rainfall compared to other schemes over the study period while the Betts-Miller-Janji’c and the Kain-Fritsch schemes overestimated rainfall. However all the schemes under predicted heavy rainfall events but the Betts-Miller-Janjic and the Kain-Fritsch schemes over predicted the light rainfall. The variation of altitude presented a noticeable change in predicted rainfall where an increase of 25% in altitude increased the probability of prediction by 6.5% which shows a key role played by altitude in convection.

Spatial and temporal variation of papyrus root mat thickness and water storage in a tropical wetland system

Papyrus wetlands are predominant in permanently inundated areas of tropical Sub Saharan Africa (SSA) and offer both provisioning and regulatory services. Although a wealth of literature exists on wetland functions, the seasonal behaviour of the papyrus mat and function in water storage has received less attention. The objective of this study was to assess the response of the papyrus root mat to changing water levels in a tropical wetland system in Eastern Uganda. We delineated seven transects through a section of a wetland system and mapped wetland bathymetry along these transects. We used three transects to measure spatial and temporal changes in mat thickness and free water column, and to monitor variations in total depth during two seasons. The free water column increased across all transects in the wet season. However, changes in the mat thickness varied spatially and were influenced by the rate of increase of the free water column as well as wetland bathymetry. The proportion of mat compression was higher at the shallow end of the wetland (83%) compared to the deep end (67%). There was a significant negative correlation between changes in free water column and papyrus mat thickness (r = -0.85, p = 000). Therefore, the mat compresses in response to increase in free water column, which increases the ratio of the free water column to root mat thickness. Hence, the wetland accommodates excess water during rainy seasons. Water depth varied from 1.5 m to 2.1 m during the monitoring period, corresponding to a water storage of 61,597 m3 and 123,355 m3 respectively. This means a 50% change in water volume for the studied wetland section. This water regulatory function mitigates severity of floods downstream, but the stored water is also useful to the surrounding communities for wetland-edge farm irrigation during dry seasons.