Determinants of woody cover in African savannas
Mahesh Sankaran
(1)
,
Niall P. Hanan
(1)
,
Robert J. Scholes
(2)
,
Jayashree Ratnam
(1)
,
David J. Augustine
(3)
,
Brian S. Cade
(4)
,
Jacques Gignoux
(5)
,
Steven I. Higgins
(6)
,
Xavier Le Roux
(7)
,
Fulco Ludwig
(8)
,
Jonas Ardo
(9)
,
Feetham Banyikwa
(10)
,
Andries Bronn
(11)
,
Gabriela Bucini
(1)
,
Kelly K. Caylor
(12)
,
Michael B. Coughenour
(1)
,
Alioune Diouf
(13)
,
Wellington Ekaya
(14)
,
Christie J. Feral
(15)
,
Edmund C. February
(16)
,
Peter G. H. Frost
(17)
,
Pierre Hiernaux
(18)
,
Halszka Hrabar
(19)
,
Kristine L. Metzger
(20)
,
Herbert H. T. Prins
(21)
,
Susan Ringrose
(22)
,
William Sea
(1)
,
Jörg Tews
(23)
,
Jeff Worden
(1)
,
Nick Zambatis
(24)
1
NREL -
Natural Resource Ecology Laboratory [Fort Collins]
2 Division of Forest Science and Technology
3 USDA Forest Service
4 US Geological Survey [Fort Collins]
5 FESE - Fonctionnement et évolution des systèmes écologiques
6 UFZ - Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research
7 LEM - Laboratoire d'Ecologie Microbienne - UMR 5557
8 CSIRO Centre for Environment and Life Sciences
9 Department of Physical Geography and Ecosystem Science [Lund]
10 Department of Botany
11 Department of Agriculture and Game Management
12 Department of Civil and Environmental Engineering
13 CSE - Centre de Suivi Ecologique [Dakar]
14 Department of Range Management
15 Environmental Sciences Department
16 Department of Botany
17 Institute of Environmental Studies
18 CESBIO - Centre d'études spatiales de la biosphère
19 University of Pretoria [South Africa]
20 Department of Zoology
21 Resource Ecology Group
22 Harry Oppenheimer Okavango Research Center
23 Plant Ecology & Nature Conservation
24 Scientific Services
2 Division of Forest Science and Technology
3 USDA Forest Service
4 US Geological Survey [Fort Collins]
5 FESE - Fonctionnement et évolution des systèmes écologiques
6 UFZ - Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research
7 LEM - Laboratoire d'Ecologie Microbienne - UMR 5557
8 CSIRO Centre for Environment and Life Sciences
9 Department of Physical Geography and Ecosystem Science [Lund]
10 Department of Botany
11 Department of Agriculture and Game Management
12 Department of Civil and Environmental Engineering
13 CSE - Centre de Suivi Ecologique [Dakar]
14 Department of Range Management
15 Environmental Sciences Department
16 Department of Botany
17 Institute of Environmental Studies
18 CESBIO - Centre d'études spatiales de la biosphère
19 University of Pretoria [South Africa]
20 Department of Zoology
21 Resource Ecology Group
22 Harry Oppenheimer Okavango Research Center
23 Plant Ecology & Nature Conservation
24 Scientific Services
Jacques Gignoux
- Fonction : Auteur
- PersonId : 9760
- IdHAL : jacques-gignoux
- ORCID : 0000-0003-3853-9282
- IdRef : 095621318
Xavier Le Roux
- Fonction : Auteur
- PersonId : 1153803
- ORCID : 0000-0001-9695-0825
- IdRef : 073278378
Résumé
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.