Savannah phenological characteristics in Karamoja sub-region, Uganda

Phenological properties such as the timing and rate of green up, aptitude and duration of vegetation growth, and timing and rate of vegetation senescence are important indicators of global environmental changes. It is vital to study these properties since savannahs play an important role in the global carbon cycle due to their global dominance on landscape level. With long term and continuous satellite observations, it is possible to monitor changes in abiotic and biotic attributes of savannahs such as phenological chracteristics and relate them to global, regional and local scale environmental changes including climatic variability and change. This study was done to determine savannah phenological characteristics in Karamoja sub-region using the Moderate-resolution Imaging Spectroradiometer (MODIS) Normalised Difference Vegetation Index (NDVI) derived data. Data processing and analysis was undertaken using TIMESAT program and ArCGIS. Results showed that representative vegetation types (varying grassland, woodland, bushland, thickets and shrubs) often had unique seasonal and interannual phenological and spatial patterns. Further, growing periods were chose as key phenophases to disuss the regional phenology patterns in Karamoja region during 2000, 2008 and 2017. Three indeces i.e., Start of the growing season (SGS), end of the growing season (EGS) and length of the growing season (LGS) were identified. The start of the growing season is variable in the sub-region but generally occurs between March – April with a clear short-term session for woodlands and grasslands in June. These two land cover types have a variable second peak period in August (Woodlands) and between September and October (grasslands). A long term time series analysis of the phenological characteristics over the sub-region is required to better indentify the internal dynamics within the land cover types.