On localized vegetation patterns, fairy circles and localized patches in arid landscapes

TL;DR

This paper explores how strong nonlocal coupling stabilizes localized vegetation patterns like fairy circles and patches in arid landscapes, providing analytical and numerical insights that align with field observations.

Contribution

It introduces a mechanism based on Lorentzian nonlocal coupling that explains the formation and stability of localized vegetation structures in arid ecosystems.

Findings

Localized dip width increases with aridity

Localized patch width decreases with aridity

Stable dip and peak structures are stabilized by nonlocal coupling

Abstract

We investigate the formation of localized structures with a varying width in one and two-dimensional systems. The mechanism of stabilization is attributed to strong nonlocal coupling mediated by a Lorentzian type of Kernel. We show that, in addition to stable dips found recently [see, e.g., C. Fernandez-Oto, M. G. Clerc, D. Escaff, and M. Tlidi, Phys. Rev. Lett. {\bf{110}}, 174101 (2013)], exist stable localized peaks which appear as a result of strong nonlocal coupling, i.e. mediated by a coupling that decays with the distance slower than an exponential. We applied this mechanism to arid ecosystems by considering a prototype model of a Nagumo type. In one-dimension, we study the front that connects the stable uniformly vegetated state with the bare one under the effect of strong nonlocal coupling. We show that strong nonlocal coupling stabilizes both---dip and peak---localized structures. We show analytically and numerically that the width of localized dip, which we interpret as fairy circle, increases strongly with the aridity parameter. This prediction is in agreement with filed observations. In addition, we predict that the width of localized patch decreases with the degree of aridity. Numerical results are in close agreement with analytical predictions.