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Determinants of woody cover in African savannas

Sankaran, M; Hanan, NP; Scholes, RJ; Ratnam, J; Augustine, DJ; Cade, BS; Gignoux, J; Higgins, SI; Le Roux, X and Ludwig, F, et al. (2005) In Nature 438(7069). p.846-849
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 we 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... (More)
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 we 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. (Less)
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Nature
volume
438
issue
7069
pages
846 - 849
publisher
Nature Publishing Group
external identifiers
  • wos:000233777800049
  • pmid:16341012
  • scopus:28644450403
ISSN
0028-0836
DOI
10.1038/nature04070
language
English
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yes
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c05d2320-b374-4a43-ad22-4a4583f285ab (old id 211470)
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2007-08-10 09:13:38
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@article{c05d2320-b374-4a43-ad22-4a4583f285ab,
  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 we 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.},
  author       = {Sankaran, M and Hanan, NP and Scholes, RJ and Ratnam, J and Augustine, DJ and Cade, BS and Gignoux, J and Higgins, SI and Le Roux, X and Ludwig, F and Ardö, Jonas and Banyikwa, F and Bronn, A and Bucini, G and Caylor, KK and Coughenour, MB and Diouf, A and Ekaya, W and Feral, CJ and February, EC and Frost, PGH and Hiernaux, P and Hrabar, H and Metzger, KL and Prins, HHT and Ringrose, S and Sea, W and Tews, J and Worden, J and Zambatis, N},
  issn         = {0028-0836},
  language     = {eng},
  number       = {7069},
  pages        = {846--849},
  publisher    = {Nature Publishing Group},
  series       = {Nature},
  title        = {Determinants of woody cover in African savannas},
  url          = {http://dx.doi.org/10.1038/nature04070},
  volume       = {438},
  year         = {2005},
}