Speaker:  Dr Caroline Lehmann, Lecturer in Biogeography, University of Edinburgh

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Ecologists have long sought to elucidate the controls on savanna vegetation structure and the limits of the biome relative to fire and climate. In seeking biome wide relationships explaining woody biomass across Australian, African and South American savannas, we found that the directional relationships among rainfall, fire and vegetation were universal. That is, increasing rainfall drives increases in both fire and tree biomass, while fire reduces tree biomass. However, among regions, the magnitude of these effects varied so substantially that a single model cannot represent global patterns of savanna woody biomass or the limits of the biome. The legacy of evolutionary and environmental differences, underpinned by regional differences in plant lineages (of both trees and grasses) and their plant traits, have cascading impacts that drives regional variation in the contemporary extent and dynamic of tropical savannas. These same differences will determine the regional response of vegetation to future climates, with substantial implications for climate induced changes in biome extent and global carbon stocks. Importantly, this work demonstrates how conservatism of plant traits within lineages scales to impact global ecology and also calls into question how we define biomes.

Caroline Lehmann works on improving our understanding of the ecology and evolution of tropical ecosystems, specifically savannas. She does this via linking remotely sensed data, experimental data, meta-analyses and field observations. Caroline currently works on projects aimed at improving our understanding of savanna vegetation dynamics and extent related to climate and fire, the evolution and assembly of C4 grasslands, improving the definition of tropical biomes, and, plant-fire coevolution.