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Speaker: Sally Archibald, Assoc Professor, Animal Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg
Fire and grazing are competing consumers: large fires reduce the spread of grazing-lawns, and heavy grazing prevents fire spread. The existence of alternative states for tropical ecosystems – fire-prone vs herbivore dominated – has long been discussed, but without much hard evidence. Sally will review the data on interactions between fire and herbivory, and discuss how feedbacks between tall-grass fire-prone ecosystems vs short-grass herbivore-dominated ecosystems could act to reinforce these different ecosystem states across environmental gradients in Africa. Key to understanding these dynamics is explaining differences in life-history characteristics of the grass species involved. She will demonstrate how strategy schemes associated with fire have impacts both on an organism’s exposure to herbivory, and its ability to tolerate herbivory, and vice versa. If the dominant consumer in many African ecosystems is not set, but can change over time in response to drought, disease or changes in management, it has implications on understanding niche construction, community assembly and ecological filtering of communities exposed to fire and herbivory.
Sally Archibald is an associate Professor at the University of the Witwatersrand. She works on understanding the dynamics of savanna ecosystems in the context of global change. Her work integrates field ecological data, remote sensing, modelling, and biogeochemistry. She is involved in collaborative research projects with Yale University, Edinburgh University and the University of Liverpool among others, which variously work on fire-grazer interactions, intercontinental savanna comparisons, the importance of land-atmosphere feedbacks, and pursuing a global theory of fire.