Description: Climate - in terms of temperature, precipitation and continentality - is a primary determinant in the distribution of African vegetation / ecosystems. Salvador Rivas-Martinez and Salvador Rivas-Saenz (2004) developed a global bioclimatic classification system that quantifies key bioclimatic indices reflective of vegetation distributions. These indices can be used to model thermotypes (i.e. hot-cold gradients), and ombrotypes (i.e. wet-dry gradients). Their model was translated into GIS spatial algorithms to produce bioclimate data for the US ecological systems mapping project (Sayre and others, 2009). These spatial models were used (with minor adaptations) with Worldclim climatological data (Hijmans et. al. 2005) to model/map African ombrotypes and thermotypes. These two datasets were then combined to produce an isobioclimate map with a total of 157 composite classes.
Description: The land surface forms were identified using the method developed by the Missouri Resource Assessment Partnership (MoRAP). The MoRAP method is an automated land surface form classification based on Hammond’s (1964a, 1964b) classification. MoRAP made modifications to Hammond’s classification, which allowed finer-resolution elevation data to be used as input data and analysis to be made using 1 km2 moving window (True, 2002; True and others, 2000). While Hammond’s methodology was based on three variables, slope, local relief, and profile type, MoRAP’s methodology uses only slope and local relief (True, 2002). Slope is classified as gently sloping or not gently sloping using a threshold value of 8%. Local relief is classified into five classes (0-15m, 16-30m, 31-90m, 91-150m, and >150m). Slope classes and relief classes were subsequently combined to produce eight land surface form classes (flat plains, smooth plains, irregular plains, escarpments, low hills, hills, breaks/foothills, and low mountains). Sayre and others (2009) further refined the MoRAP methodology to identify a new land surface form class, “high mountains/deep canyons”, by using an additional local relief class (>400 m). The Africa implementation used a 90-meter elevation dataset which was created by void-filling and re-sampling the 30-meter SRTM elevation data provided by the National Geospatial- Intelligence Agency.
Description: The African surficial lithology dataset is a map of parent materials - a mix of bedrock geology and unconsolidated surficial materials classes. The goal was to produce a map that reflected the key geological parent materials which act as primary determinants in the distribution of African vegetation /ecosystems. It is a compilation and reclassification of twelve digital geology, soil and lithology databases. Nineteen surficial lithology classes were delineated in Africa based on geology, soil and landform. Whenever available, multiple sources of ancillary digital data, hard copy maps and literature were reviewed to assist in the reclassification of the source data to the African surficial lithology classification. Of particular note, due to the varying spatial and classification resolutions of the geologic source data, the African surficial lithology map varies in spatial complexity and classification detail across Africa.