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| HAL : halsde-00304266, version 1 |
| DOI : 10.1038/nature04070 |
| Fiche détaillée |  Récupérer au format |
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| Nature 438, 8 (2005) 846-849 |
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| Determinants of woody cover in African savannas |
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| Mahesh Sankaran 1Niall P. Hanan 1 |
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| (2005) |
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| Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties1–3. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover1,2,4,5, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than ,650mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered ‘stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of ,650mm, savannas are ‘unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation6 may considerably affect their distribution and dynamics. |
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| 1 : | Natural Resource Ecology Laboratory |
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University of Colorado |
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| 2 : | Division of Forest Science and Technology |
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Division of Forest Science and Technology |
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| 3 : | USDA Forest Service |
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Commanche National Grassland |
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| 4 : | US Geological Survey |
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Fort Collins Science Center |
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| 5 : | Fonctionnement et évolution des systèmes écologiques (FESE) |
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CNRS : UMR7625 – Université Pierre et Marie Curie [UPMC] - Paris VI – Ecole normale supérieure de Paris - ENS Paris |
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| 6 : | Umweltforschungszentrum Leipzig Halle |
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Sekt Okosyst Anal |
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| 7 : | Ecologie microbienne (EM) |
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CNRS : UMR5557 – Institut national de la recherche agronomique (INRA) : UR1193 – Université Claude Bernard - Lyon I – Ecole Nationale Vétérinaire de Lyon |
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| 8 : | CSIRO Centre for Environment and Life Sciences |
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CSIRO |
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| 9 : | Department of Physical Geography and Ecosystems Analysis |
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Lund University |
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| 10 : | Department of Botany |
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University of Dar es Salaam |
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| 11 : | Department of Agriculture and Game Management |
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Port Elizabeth Technikon |
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| 12 : | Department of Civil and Environmental Engineering |
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Princeton University |
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| 13 : | Centre de Suivi Ecologique |
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Centre de Suivi Ecologique |
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| 14 : | Department of Range Management |
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University of Nairobi |
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| 15 : | Environmental Sciences Department |
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University of Virginia |
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| 16 : | Department of Botany |
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University of Cape Town |
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| 17 : | Institute of Environmental Studies |
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University of Zimbabwe |
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| 18 : | Centre d'études spatiales de la biosphère (CESBIO) |
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CNRS : UMR5126 – Institut de recherche pour le développement [IRD] – CNES – Observatoire Midi-Pyrénées – INSU – Université Paul Sabatier [UPS] - Toulouse III |
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| 19 : | Mammal Research Institute |
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University of Pretoria |
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| 20 : | Department of Zoology |
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University of Wisconsin |
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| 21 : | Resource Ecology Group |
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wageningen University |
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| 22 : | Harry Oppenheimer Okavango Research Center |
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University of Botswana |
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| 23 : | Plant Ecology & Nature Conservation |
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University of Postdam |
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| 24 : | Scientific Services |
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Kruger National Park |
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| domaine | : | Sciences du Vivant/Ecologie, Environnement Sciences du Vivant/Biodiversité Sciences de l'environnement/Biodiversité et Ecologie |
| halsde-00304266, version 1 | |
| http://hal-sde.archives-ouvertes.fr/halsde-00304266 | |
| oai:hal-sde.archives-ouvertes.fr:halsde-00304266 | |
| Contributeur : Christine Delorme | |
| Soumis le : Mardi 22 Juillet 2008, 16:25:36 | |
| Dernière modification le : Mercredi 23 Juillet 2008, 11:12:36 | |
