Spiral vegetation patterns in high-altitude wetlands |
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| Institution: | 1. Institut de Recherche pour le Développement (IRD), UMR-AMAP, TA A-51/PS2, 34398 Montpellier Cedex 05, France;2. French Institute of Pondicherry (IFP), 11 Saint Louis Street, 605001 Pondicherry, India;3. Instituto de Ecología, Universidad Mayor San Andrés, Casilla 10077, Correo Central, La Paz, Bolivia;4. Museo Nacional de Historia Natural, Herbario Nacional de Bolivia (LPB), Cota Cota, Casilla 10077 Correo Central, La Paz, Bolivia;5. Université Grenoble Alpes, LECA, Laboratoire d’Écologie Alpine, CS 40700, 38058 Grenoble Cedex 9, France;1. Department of Physical Chemistry and Materials Science, University of Szeged, Aradi vértanúk tere 1, Szeged H-6720, Hungary;2. Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary;1. Department of Computer Science, School of Electrical and Computer Engineering, National Defense Academy of Japan, 1-10-20 Hashirimizu, Yokosuka, Kanagawa, 239-8686, Japan;2. Department of Intelligent Interaction Technologies, Graduate School of Systems and Information Engineering, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 386-8567, Japan;1. Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA;2. Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA;3. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA;4. Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA;5. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA;6. Ecole Polytechnique Federale de Lausanne, Station 2, CH-1015 Lausanne, Switzerland;7. Cooperative Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, Boulder, CO 80309, USA;8. Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA |
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| Abstract: | When plant communities suffer the stress of limited resources, for instance adverse environmental conditions such as extreme aridity, the spatial homogeneity of the biomass is lost and self-organized patterns may arise. Here, we report the observation of spiral-shaped patterns in the biomass of grass (genus deyeuxia), under highland arid conditions in the north of Chile. The spiral arms are a few meters long and a few centimeters wide. These dynamic structures are observed in the grazing area of an herbivore member of the South American camelids, the vicuna, on the border of highland wetlands. These spirals cannot be explained by the well-established mathematical models which describe other vegetation patterns (that emerge from a Turing-type of instability) such as stripes, rings, or fairy circles. We attribute the formation of spirals to the coupling between the growth of vegetation in semiarid regions and the grazing of vicunas. The mathematical analysis of this coupling reveals an excitable behavior, i.e. small perturbations of the equilibrium generate large trajectories before coming back, that is the origin of the spirals. |
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