A model for the explanation of vegetation stripes (tiger bush)

Regular vegetation patterns appear on aerial views of plateaux in SW Niger where densely and sparsely populated zones alternate with each other. This spatial organization of the vegetation is an endogenous phenomenon which is not limited to specific plants or soils; it is a characteristic landscape of many arid regions throughout the world. The phenomenon is interpreted as the result of a spatial range difference between two biologically distinct interactions operating at the plant population level. The proposed mechanism is independent of external heterogeneities deriving from soil geomorphology or meteorology. We present a model to simulate the genesis of vegetation stripes. In addition, the model predicts the occurrence of vegetation hexagons corresponding to higher or lower density spots arranged in a hexagonal lattice. The distinction between the two spatial symmetries is discussed in terms of their Fourier transforms.