Spatial self-organisation enables species coexistence in a model for savanna ecosystems

L. Eigentler, J. A. Sherratt

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The savanna biome is characterised by a continuous vegetation cover, comprised of herbaceous and woody plants. The coexistence of species in arid savannas, where water availability is the main limiting resource for plant growth, provides an apparent contradiction to the classical principle of competitive exclusion. Previous theoretical work using nonspatial models has focussed on the development of an understanding of coexistence mechanisms through the consideration of resource niche separation and ecosystem disturbances. In this paper, we propose that a spatial self-organisation principle, caused by a positive feedback between local vegetation growth and water redistribution, is sufficient for species coexistence in savanna ecosystems. We propose a spatiotemporal ecohydrological model of partial differential equations, based on the Klausmeier reaction-advection-diffusion model for vegetation patterns, to investigate the effects of spatial interactions on species coexistence on sloped terrain. Our results suggest that species coexistence is a possible model outcome, if a balance is kept between the species’ average fitness (a measure of a species’ competitive abilities in a spatially uniform setting) and their colonisation abilities. Spatial heterogeneities in resource availability are utilised by the superior coloniser (grasses), before it is outcompeted by the species of higher average fitness (trees). A stability analysis of the spatially nonuniform coexistence solutions further suggests that grasses act as ecosystem engineers and facilitate the formation of a continuous tree cover for precipitation levels unable to support a uniform tree density in the absence of a grass species.
Original languageEnglish
Article number110122
JournalJournal of Theoretical Biology
Volume487
Early online date17 Dec 2019
DOIs
Publication statusPublished - 21 Feb 2020

Keywords

  • Banded vegetation
  • Ecosystem engineering
  • Pattern formation
  • Periodic travelling waves
  • Reaction-advection-diffusion
  • Spectral stability
  • Tiger bush
  • Vegetation patterns
  • Wavetrains

ASJC Scopus subject areas

  • Statistics and Probability
  • Modelling and Simulation
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Agricultural and Biological Sciences(all)
  • Applied Mathematics

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