Spatial analysis and modeling of carbon storage in native shrubs of Senegal's Peanut Basin
Farmlands, grasslands, and savannas in semi-arid sub-Sahelian Africa have the potential to store carbon (C) in soil. There is a great need to manage ecosystems to increase C storage in semi-permanent soil pools. This will improve soil quality, impede desertification and by reducing atmospheric CO 2 levels, will slow climate change. Several previous studies highlight the role of trees as a source of C to the soils of Senegal's Peanut Basin. This study is the first to recognize the role of Guiera senegalensis and Piliostigma reticulatum (two native shrub species widely found in natural and agro-ecosystems in sub-Sahelian Africa), as key vegetative C sink in this landscape. This dissertation reports on three components of study. First, investigation of factors mediating distribution and total abundance of these shrubs shows that shrub distribution is controlled by geological substrate, mean annual temperature, mean annual rainfall and terrain profile convexity. Relative abundance of shrubs within their communities is influenced by mean annual rainfall, maximum annual temperature and elevation (for G. senegalensis ) and mean annual rainfall, mean annual temperature, elevation and profile convexity (for P. reticulatum ). The second study reports on the biomass C stocks of the shrubs and the relative influence of the shrubs and trees on spatial dependence of soil C levels. Estimates of peak-season biomass C ranged from 0.9 to 1.4 Mg C ha-1 with an overall mean of 1.12 Mg C ha-1 (SEM = ±0.079) where G. senegalensis dominates and from 1.3 to 2.0 Mg C ha-1 (mean = 1.57 Mg C ha-1 ; SEM = ±0.18) where P. reticulatum dominates. Geostatistical analyses showed that shrubs had greater influence on landscape-level soil C levels than trees. The third study presents the regional C stocks and development of a method that couples the CENTURY model and GIS to model C dynamics for G. senegalensis in a portion of the basin. There is approximately 247000 Mg of biomass C at peak-season for the studied section and CENTURY model projections indicate that C sequestration in the area is hinged on long-term effectiveness of fire suppression (through residue burning) with actual rates depending strongly on scenarios of management and soil type.*
*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation).
0481: Soil sciences