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Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/2072

Title: Determinants of woody cover in African savannas
Authors: Sankaran, M
Hanan, NP
Scholes, RJ
Ratnam, J
Augustine, DJ
Cade, BS
Gignoux, J
Higgins, SI
Le Roux, X
Ludwig, F
Ardo, J
Banyikwa, F
Bronn, A
Bucini, G
Caylor, KK
Coughenour, MB
Diouf, A
Ekaya, W
Feral, CJ
February, EC
Frost, PGH
Hiernaux, P
Hrabar, H
Metzger, KL
Prins, HHT
Ringrose, S
Sea, W
Tews, J
Worden, J
Zambatis, N
Keywords: Wood covers
Savanna structures
Resource availability
Mammalian herbivory
Disturbance regimes
African savannas
Multidisciplinary sciences
Issue Date: 8-Dec-2005
Publisher: Nature Publishing Group
Citation: Sankaran, M, et al. 2005. Determinants of woody cover in African savannas. Nature, vol. 438(7069), pp 846-869
Abstract: 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 properties (1-3). The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover (1,2,4,5), but perceptions differ on which of these are the primary drivers of savanna structure. Here the authors show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than similar to 650 mm 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 similar to 650 mm, 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 precipitation (6) may considerably affect their distribution and dynamics.
URI: http://hdl.handle.net/10204/2072
ISSN: 0028-0836
Appears in Collections:Forestry and wood science
General science, engineering & technology

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