Graduate Exit Seminar

Matthew Bright will present his Graduate Exit Seminar at 2:00 p.m. in 333C Kottman Hall. His presentation is The Role of Shrub Agroforestry Systems in Increasing Food Security for the West African Sahel.

The West African Sahel (WAS) faces environmental and socioeconomic constraints that routinely threaten regional food security. This dissertation examined the use of a ubiquitous and increasing component of the region’s natural savanna ecosystem – native shrubs – to enhance the growth and yields of the staple crops, pearl millet (Pennisetum glaucum) and groundnut (Arachis hypogeae).  We found that growing crops for eleven years next to high densities of two shrubs, Guiera senegalensis and Piliostigma reticulatum, increased yields dramatically over crops in bare soils with synthetic fertilizer inputs.  Furthermore, the shrubs improved soil quality: fertility, carbon, water holding capacity, and water use efficiency.  The ecological mechanisms behind the increased crop growth (shrub root growth patterns and water infiltration) were also examined and revealed novel insights into why shrubs do not compete with crops. We additionally investigated arbuscular mycorrhizal fungal (a group of beneficial symbiotic fungi) communities in the G. senegalensis intercropping system and report the importance of these soil microorganisms to millet production in this semi-arid environment. A review of all shrubs in the WAS, showed that potentially many species, in addition to P. reticulatum and G. senegalensis, could be used to increase crop yields. Overall, the results suggest that the increasing dominance of shrubs across the Sahel and their unique ecological adaptation to farming make them keystone species critical for increasing food security and mitigating the detrimental effects of climate change in the region.