Patterns as indicators of productivity enhancement by facilitation and competition in dryland vegetation

[1] Well-defined vegetation patterns are a widespread feature of dryland landscapes, where spotted, banded, or other organized systems of vegetation patches are bordered by bare soil. A number of different mechanisms have been invoked to explain the emergence of these patterns and to associate their geometrical features to the driving (biotic and abiotic) processes. A commonly accepted theory of pattern formation is based on the interplay between mechanisms of short-range facilitation and long-range competition with surrounding vegetation. Recently associated with the emergence of vegetation patterns, these shortand long-range interactions have been seldom interpreted as a means for plants to enhance their chances of survival in arid environments. Here we develop a simplistic facilitation-competition model to show how these spatial interactions increase the productivity of dryland ecosystems. Stable (sparsely) vegetated states are shown to occur even in systems in which unvegetated conditions are the only stable state of the local dynamics (i.e., in the absence of spatial interaction). Pattern emergence is also interpreted as an easily detectable sign of the occurrence of highly effective resource allocation and use due to spatial interactions. Moreover, the resilience of vegetated states is qualitatively related to pattern geometry.