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Determinants of woody encroachment in savannas: A comparison between South American and Africa

Lucía Sol Mochi

University of Georgia

The process of woody encroachment in savannas has significantly increased during the last century; it occurs throughout a wide range of environmental conditions; including arid, semi-arid and humid systems with different biogeographic histories. Its consequences are diverse (e.g. changes in species composition, in biogeochemical cycles, in habitat for fauna and in the provision of ecosystem services, among others). Although the importance of rainfall and grazing as regulators of the process is well known, conclusions at global scale are not yet elucidated. The objective of this project is to explore and compare drivers of encroachment in savannas through a climatic and evolutionary range in South America and Africa. This approach would permit me to elucidate wich mechanisms operate at an intercontinental scale and wich are our own contingencies or exclusive to the savanna ecosystems of our country. I (advised by Dra. Noemi Mazia, UBA) and, simultaneously, Dr. Ricardo Holdo (Odum School of Ecology, UGA) and colleagues have carried out a set of sowing and transplanting comparable experiments in these two continents, by wich we study the demographic controls of four species of Acacia. During the proposed stay I plan to: 1) work in a joint analysis of experimental data analysis of the results of our experiments leading to generate knowledge about the determining mechanisms of the process of encroachment in both continents; 2) elaborate a meta-analysis of experimental to deepen the knowledge of this process and 3) through these two approaches, work on a protocol to implement new a posteriori comparable experiments in other savanna systems in both continents thus giving rise to a network of comparable tests. This project represents a novel approach to savanna ecology especially focused on a first-time comparison between Argentinian and African savannas. The results of this project have potential implications for the sustainability of the inhabitants of these regions, inasmuch as woody encroachment affects cattle raising (subsistence livestock in many places of the region).

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