Citation

Calabrese JM, Vazquez F, Lopez C, San Miguel M, Grimm V. Am. Nat. 2010; 175(3): E44-65.

Affiliation

1. Department of Ecological Modelling, Helmholtz Centre for Environmental Research (UFZ), Permoserstrasse 15, 04318 Leipzig, Germany;

Copyright

(Copyright © 2010, University of Chicago Press)

DOI

10.1086/650368

PMID

20100108

Abstract

Savanna ecosystems are widespread and economically important and harbor considerable biodiversity. Despite extensive study, the mechanisms regulating savanna tree populations are not well understood. Recent empirical work suggests that both tree-tree competition and fire are key factors in semiarid to mesic savannas, but the potential for competition to structure savannas, particularly in interaction with fire, has received little theoretical attention. We develop a minimalistic and analytically tractable stochastic cellular automaton to study the individual and combined effects of these two factors on savannas. We find that while competition often substantially depresses tree density, fire generally has little effect but can drive tree extinction in extreme scenarios. When combined, competition and fire interact nonlinearly with strong negative consequences for tree density. This novel result may help explain observed variability among apparently similar savannas in their response to fire. Paradoxically, this interaction could also render the presence of competition more difficult to detect in empirical studies because fire can override the characteristic regular spacing driven by competition and lead instead to clustering.

Language: en