COLLABORATIVE RESEARCH: Mechanisms of tree recruitment limitation across a savanna soil moisture availability gradient

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Tropical grasslands, or savannas, cover over 20 percent of the land on Earth, support most of the world's livestock and wild herbivores, and thus feed a large fraction of the world's population. At their edges, savannas often grade into forest, and they can shrink or expand depending on whether the forests advance or retreat. Three major factors seem likely to account for the boundary between savanna and forest: fire that kills trees, rainfall that sustains them, and the grazing of the herbivores on tree seedlings and grass. This project will mount a very large field experiment in one of the most productive savannas in the world, the Serengeti of Tanzania, to test which combinations of fire, water, and grazing best maintain savanna. Researchers from the U.S. and Tanzania will plant seeds and seedlings of dominant trees into fenced or unfenced, and burned or unburned areas within different sites that range from low to high rainfall, and then measure the success of the trees over three years.Besides giving us new understanding of why savannas occur where they do and how their boundaries may change in the future, knowledge important to our ability to manage livestock and provide food, this research will train new scientists, promote international collaboration, and build the capacity for science in the developing world. The project will help train two Tanzanian researchers plus a Tanzanian graduate student at the University of Missouri and a postdoctoral scholar at Wake Forest University in North Carolina. To build scientific capacity in Africa, the project will offer annual workshops on data collection and statistics for students at Tanzania's Sokoine University of Agriculture.