title: Regime shifts in models of dryland vegetation.
abstract: Drylands are pattern-forming systems showing self-organized vegetation patchiness, multiplicity of stable states and fronts separating domains of alternative stable states. Pattern dynamics, induced by droughts or disturbances, can result in desertification shifts from patterned vegetation to bare soil. Pattern formation theory suggests various scenarios for such dynamics: an abrupt global shift involving a fast collapse to bare soil, a gradual global shift involving the expansion and coalescence of bare-soil domains and an incipient shift to a hybrid state consisting of stationary bare-soil domains in an otherwise periodic pattern. Using models of dryland vegetation, we address the question of which of these scenarios can be realized. We found that the models can be split into two groups: models that exhibit multiplicity of periodic-pattern and bare-soil states, and models that exhibit, in addition, multiplicity of hybrid states. Furthermore, in all models, we could not identify parameter regimes in which bare-soil domains expand into vegetated domains. The significance of these findings is that, while models belonging to the first group can only exhibit abrupt shifts, models belonging to the second group can also exhibit gradual and incipient shifts. A discussion of open problems concludes the paper.
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.forename: Shai
authors.initials: S
authors.lastname: Kinast
authors.forename: Hezi
authors.initials: H
authors.lastname: Yizhaq
authors.forename: Golan
authors.initials: G
authors.lastname: Bel
authors.forename: Ehud
authors.initials: E
authors.lastname: Meron
mesh_terms: D003247:Conservation of Natural Resources; D017753:Ecosystem; D008954:Models, Biological; D008962:Models, Theoretical; D011891:Rain; D012987:Soil
chemical_list: D012987:Soil
keywords: desertification; fronts; homoclinic snaking; localizedpatterns; models of vegetation pattern formation; multiplicity of stable states