Document Detail

Spatial vegetation patterns and imminent desertification in Mediterranean arid ecosystems.
MedLine Citation:
PMID:  17851524     Owner:  NLM     Status:  MEDLINE    
Humans and climate affect ecosystems and their services, which may involve continuous and discontinuous transitions from one stable state to another. Discontinuous transitions are abrupt, irreversible and among the most catastrophic changes of ecosystems identified. For terrestrial ecosystems, it has been hypothesized that vegetation patchiness could be used as a signature of imminent transitions. Here, we analyse how vegetation patchiness changes in arid ecosystems with different grazing pressures, using both field data and a modelling approach. In the modelling approach, we extrapolated our analysis to even higher grazing pressures to investigate the vegetation patchiness when desertification is imminent. In three arid Mediterranean ecosystems in Spain, Greece and Morocco, we found that the patch-size distribution of the vegetation follows a power law. Using a stochastic cellular automaton model, we show that local positive interactions among plants can explain such power-law distributions. Furthermore, with increasing grazing pressure, the field data revealed consistent deviations from power laws. Increased grazing pressure leads to similar deviations in the model. When grazing was further increased in the model, we found that these deviations always and only occurred close to transition to desert, independent of the type of transition, and regardless of the vegetation cover. Therefore, we propose that patch-size distributions may be a warning signal for the onset of desertification.
Sonia Kéfi; Max Rietkerk; Concepción L Alados; Yolanda Pueyo; Vasilios P Papanastasis; Ahmed Elaich; Peter C de Ruiter
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Nature     Volume:  449     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2007 Sep 
Date Detail:
Created Date:  2007-09-13     Completed Date:  2007-10-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  213-7     Citation Subset:  IM    
Department of Environmental Sciences, Copernicus Institute, Utrecht University, PO Box 80115, 3508 TC Utrecht, The Netherlands.
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MeSH Terms
Desert Climate*
Mediterranean Region
Models, Biological
Plants / growth & development*
Population Dynamics
Stochastic Processes
Comment In:
Nature. 2007 Sep 13;449(7159):151-3   [PMID:  17851503 ]

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