title: Discovery of fairy circles in Australia supports self-organization theory.
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.
authors.affiliation: Department of Ecological Modelling, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Germany; stephan.getzin@ufz.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Getzin
authors.affiliation: 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;
authors.forename: Hezi
authors.initials: H
authors.lastname: Yizhaq
authors.affiliation: Environmental Management, Rio Tinto, Perth, WA 6000, Australia;
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Bell
authors.affiliation: 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;
authors.forename: Todd E
authors.initials: TE
authors.lastname: Erickson
authors.affiliation: P.O. Box 5473, Cairns, QLD 4870, Australia;
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Postle
authors.affiliation: Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel;
authors.forename: Itzhak
authors.initials: I
authors.lastname: Katra
authors.affiliation: Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel;
authors.forename: Omer
authors.initials: O
authors.lastname: Tzuk
authors.affiliation: Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel;
authors.forename: Yuval R
authors.initials: YR
authors.lastname: Zelnik
authors.affiliation: Department of Ecosystem Modelling, University of Goettingen, 37077 Goettingen, Germany;
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wiegand
authors.affiliation: 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.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Wiegand
authors.affiliation: 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;
authors.forename: Ehud
authors.initials: E
authors.lastname: Meron
mesh_terms: D018533:Biomass; D025461:Feedback, Physiological; D065948:Grassland; D008954:Models, Biological; D009276:Namibia; D063245:Plant Development; D006109:Poaceae / Q000254:growth & development*; D011891:Rain; D014904:Western Australia
keywords: Triodia grass; Turing instability; drylands; spatial pattern; vegetation gap