Patch structure, dynamics and implications for the functioning of arid ecosystems.

Arid ecosystems present a two-phase mosaic structure of high- and low-cover patches. Vegetation patches differ among ecosystems in size and shape. However, recent studies indicate striking similarities in patch dynamics and in mechanisms explaining their origin and maintenance. Two major types of system, banded and spotted vegetation, which are characterized by patch shape, both originate from common mechanisms, although each is dominated by a different driver. Banded vegetation occurs when water is the dominant driver of the redistribution of materials and propagules, whereas spotted vegetation results when wind is the major redistribution driver. Model analysis indicates that patchy vegetation structure enhances primary production.