Savannas are defined by the simultaneous presence of trees (or woody shrubs) and grasses in seasonally dry areas of the tropics and sub-tropics. This coexistence of very different types of plants is important in terms of the functioning of the ecosystem (e.g., vegetation growth, water use, carbon storage), but also in terms of how humans benefit from and manage these unique systems (e.g., grazing cattle or fuel-wood harvest). In Africa, savannas are key areas of economic, cultural and bio-diversity. The US and Malian collaborators in this project have designed a comprehensive field experiment to examine interactive effects of fire and large herbivores at five sites across the West African rainfall gradient, from dry Sahel in the north to wetter savannas in the south. At each site, fences and fire-breaks exclude domestic livestock or fires, respectively, from experimental plots. The team will monitor vegetation growth to examine how these disturbances affect survival and growth of trees and grasses, alter plant species composition, and differ in their effects across the rainfall gradient. The experiment will provide much needed empirical data on tree-grass interactions in West African savannas and complement research elsewhere in Africa, Australia and South America. This work thus will contribute to development of ecological theory for savannas and a better understanding of the role of disturbance in plant species coexistence.
The Sahel-Sudan zone of West Africa is crucial for the economies of Africa north of the equator and for the livelihoods of the region's pastoral and agricultural peoples. The region is subject to frequent drought, with problems of food security, environmental degradation, and desertification. An understanding of how human management practices impact ecological processes will enhance sound management in the face of future changing climate. The project will provide unique research experiences and international scientific/cultural exposure to US and African students, and facilitate development of a collaborating nucleus of African and US researchers that will endure well into the future. This award is co-funded by NSF's Office of International Science and Engineering.
