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Proc Natl Acad Sci U S A. 2016 Mar 29;113(13):3551-6. doi: 10.1073/pnas.1522130113. Epub 2016 Mar 14.

Discovery of fairy circles in Australia supports self-organization theory.

Author information

1
Department of Ecological Modelling, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Germany; stephan.getzin@ufz.de.
2
Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel; The Dead-Sea and Arava Science Center, Tamar Regional Council, Israel;
3
Environmental Management, Rio Tinto, Perth, WA 6000, Australia;
4
School of Plant Biology, The University of Western Australia, Crawley, WA 6009, Australia; Kings Park and Botanic Garden, Botanic Gardens & Parks Authority, Kings Park, WA 6005, Australia;
5
P.O. Box 5473, Cairns, QLD 4870, Australia;
6
Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel;
7
Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel;
8
Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel;
9
Department of Ecosystem Modelling, University of Goettingen, 37077 Goettingen, Germany;
10
Department of Ecological Modelling, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Germany; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, 04103 Leipzig, Germany.
11
Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel; Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel;

Abstract

Vegetation gap patterns in arid grasslands, such as the "fairy circles" of Namibia, are one of nature's greatest mysteries and subject to a lively debate on their origin. They are characterized by small-scale hexagonal ordering of circular bare-soil gaps that persists uniformly in the landscape scale to form a homogeneous distribution. Pattern-formation theory predicts that such highly ordered gap patterns should be found also in other water-limited systems across the globe, even if the mechanisms of their formation are different. Here we report that so far unknown fairy circles with the same spatial structure exist 10,000 km away from Namibia in the remote outback of Australia. Combining fieldwork, remote sensing, spatial pattern analysis, and process-based mathematical modeling, we demonstrate that these patterns emerge by self-organization, with no correlation with termite activity; the driving mechanism is a positive biomass-water feedback associated with water runoff and biomass-dependent infiltration rates. The remarkable match between the patterns of Australian and Namibian fairy circles and model results indicate that both patterns emerge from a nonuniform stationary instability, supporting a central universality principle of pattern-formation theory. Applied to the context of dryland vegetation, this principle predicts that different systems that go through the same instability type will show similar vegetation patterns even if the feedback mechanisms and resulting soil-water distributions are different, as we indeed found by comparing the Australian and the Namibian fairy-circle ecosystems. These results suggest that biomass-water feedbacks and resultant vegetation gap patterns are likely more common in remote drylands than is currently known.

KEYWORDS:

Triodia grass; Turing instability; drylands; spatial pattern; vegetation gap

PMID:
26976567
PMCID:
PMC4822591
DOI:
10.1073/pnas.1522130113
[Indexed for MEDLINE]
Free PMC Article

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