Drylands, regions with an Aridity Index (i.e., the ratio of mean annual precipitation to mean annual potential evapotranspiration) below 0.65 , have a climate characterized by infrequent, highly variable, rainfall and intense solar radiation. Consequently, these areas experience conditions of chronic water shortage, and, unlike mesic ecosystems, do not sustain a continuous cover by vascular plants .. Given the role of water as the main limiting resource for biological activity in drylands, it is not surprising to find that a high proportion of research has focused on understanding how rainfall amount and frequency affect ecological processes in these ecosystems . The importance of climatic factors as drivers of the structure and functioning of drylands is widely accepted. The library has a hard copy