Evolutionary and Ecological Biome Switches at Tropical Savanna-Forest Boundaries

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Online seminar followed by Q&A – all welcome. (NB – all times given in UK time)

Savanna and closed-canopy forests are the two most important tropical biomes in terms of species diversity, carbon stocks, and use by humans, so there is considerable interest in understanding the current distribution of these biomes. However, due to strong positive feedbacks between vegetation and fire, we are unlikely to find simple deterministic relationships that can explain current distributions or predict future distributions. As Prof Hoffman will argue here, understanding the distribution of these biomes requires greater attention to the processes and conditions that cause shifts from savanna to forest or vice versa. In this talk, he will present results from his studies in the savannas and forests of central Brazil aimed at 1) quantifying demographic and ecosystem thresholds that govern the transition from one biome to the other, 2) understanding how climate and soils mediate the rates at which these thresholds are reached, and 3) understanding the unique roles of savanna and forest tree species in biome switches. Overall, our results demonstrate the importance of fire for the origin and maintenance of savanna ecosystems while emphasizing the need for a detailed understanding of how fire interacts with other factors to govern the distribution of savanna and forest across the tropics.

Bill Hoffmann has worked on the ecology of tropical savannas and forests of central Brazil since 1991. He obtained his PhD from Harvard University, then went on to postdoc positions at the University of Texas and then the University of Brasilia. He continued at the University of Brasilia for four years as a visiting professor before beginning his current position at North Carolina State University.