1. Floristic evidence for alternative biome states in tropical Africa
- Author
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Aleman, J. C., Fayolle, A., Favier, C., Staver, A. C., Dexter, K. G., Ryan, C. M., Azihou, A. F., Bauman, D., Te Beest, M., Chidumayo, E. N., Comiskey, J. A., Cromsigt, J. P. G. M., Dessard, H., Doucet, J.-l., Finckh, M., Gillet, J.-f., Gourlet-fleury, S., Hempson, G. P., Holdo, R. M., Kirunda, B., Kouame, F. N., Mahy, G., Gonçalves, F. Maiato P., Mcnicol, I., Quintano, P. Nieto, Plumptre, A. J., Pritchard, R. C., Revermann, R., Schmitt, C. B., Swemmer, A. M., Talila, H., Woollen, E., Swaine, M. D., Spatial Ecology and Global Change, Environmental Sciences, Gembloux Agro-Bio Tech [Gembloux], Université de Liège, Département de géographie, Université de Montréal, Montréal, Canada, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Department of Ecology and Evolutionary Biology, Yale University, School of Geosciences [Edinburgh], University of Edinburgh, Royal Botanical Garden Edinburgh, Royal Botanical Garden, Laboratory of Applied Ecology, Université d’Abomey-Calavi (UAC), School of Geography and the Environment [Oxford] (SoGE), University of Oxford [Oxford], Plant Ecology and Biogeochemistry, Faculté des Sciences [Bruxelles] (ULB), Université libre de Bruxelles (ULB)-Université libre de Bruxelles (ULB), Copernicus Institute for Sustainable Development, Utrecht University [Utrecht], Centre for African Conservation Ecology, Nelson Mandela Metropolitan University [Port Elizabeth, South Africa], Grasslands-Wetlands-Forests Node, SAEON, Makeni Savanna Research Project, Inventory & Monitoring Program, National Park Service, Smithonian Institution, Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences (SLU), Forêts et Sociétés (UPR Forêts et Sociétés), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Département Environnements et Sociétés (Cirad-ES), Institute of Plant Science and Microbiology, University of Hamburg, Odum School of Ecology, University of Georgia [USA], Wildlife Conservation Society (WCS), Université Nangui Abrogoua, Herbário do Lubango, Instituto Superior de Ciências da Educação da Huíla, Department of Zoology [Cambridge], University of Cambridge [UK] (CAM), Global Development Institute, University of Manchester [Manchester], Faculty of Natural Resources and Spatial Sciences, Namibia University of Science and Technology (NUST), University of Bonn, Chair for Nature Conservation and Landscape Ecology, South African Environmental Observation Network [Pretoria] (SAEON), College of Agriculture and Natural Resource, Madda Walabu University, Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS), Royal Botanic Garden [Edinburgh], Université d’Abomey-Calavi = University of Abomey Calavi (UAC), University of Oxford, Nelson Mandela University [Port Elizabeth], Université Nangui Abrogoua (UNA), Universität Bonn = University of Bonn, and Biotechnology and Biological Sciences Research Council (BBSRC)-Aberystwyth University
- Subjects
F40 - Écologie végétale ,Climate ,Rain ,forêt tropicale ,Forests ,compostion ,Fires ,Trees ,données spatiales ,tree species ,Alternative stable states ,Savane ,Ecosystem ,Tropical Climate ,tropical biomes ,precipitation and seasonality ,F70 - Taxonomie végétale et phytogéographie ,Biological Sciences ,Grassland ,cartographie des fonctions de la forêt ,Succession végétale ,Africa ,Écosystème forestier ,Seasons ,[SDE.BE]Environmental Sciences/Biodiversity and Ecology ,fire ,Communauté végétale ,Index de végétation - Abstract
International audience; The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited however and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa, using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleo-ecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs savanna specialists, with some generalist species that span both biomes. In conjunction with geo-referenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states, but also provide novel empirical evidence for broad scale bistability. Significance statement: We develop a biogeographic approach to analyzing the presence of alternative stable states in tropical biomes. Whilst forest-savanna bistability has been widely hypothesized and modeled, empirical evidence has remained scarce and controversial, and here, applying our method to Africa, we provide large scale evidence that there are alternative states in tree species composition of tropical vegetation. Furthermore, our results have produced novel and more accurate maps of the forest and savanna distributions in Africa, which takes into account differences in tree species composition, and a complex suite of determinants. This result is not only important for understanding the biogeography of the continent, but also to guide large-scaled tree planting and restoration efforts planned for the region.
- Published
- 2020