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Emerged or imposed: a theory on the role of physical templates and self-organisation for vegetation patchiness

Authors

  • Efrat Sheffer,

    Corresponding author
    • Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
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  • Jost von Hardenberg,

    1. ISAC-CNR, Torino, Italy
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  • Hezi Yizhaq,

    1. Department of Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben Gurion University, Israel
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  • Moshe Shachak,

    1. Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel
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  • Ehud Meron

    1. Department of Solar Energy and Environmental physics, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel
    2. Physics department, Ben-Gurion University of the Negev, Beer Sheva, Israel
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Correspondence: E-mail: efrat.sheffer@mail.huji.ac.il

Abstract

In this article, we develop a unifying framework for the understanding of spatial vegetation patterns in heterogeneous landscapes. While much recent research has focused on self-organised vegetation the prevailing view is still that biological patchiness is mostly due to top-down control by the physical landscape template, disturbances or predators. We suggest that vegetation patchiness in real landscapes is controlled both by the physical template and by self-organisation simultaneously, and introduce a conceptual model for the relative roles of the two mechanisms. The model considers four factors that control whether vegetation patchiness is emerged or imposed: soil patch size, plant size, resource input and resource availability. The last three factors determine the plant-patch size, and the plant-to-soil patch size ratio determines the impact of self-organisation, which becomes important when this ratio is sufficiently small. A field study and numerical simulations of a mathematical model support the conceptual model and give further insight by providing examples of self-organised and template-controlled vegetation patterns co-occurring in the same landscape. We conclude that real landscapes are generally mixtures of template-induced and self-organised patchiness. Patchiness variability increases due to source–sink resource relations, and decreases for species of larger patch sizes.

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