   deserts and xeric shrublands also called xerÃ³fila are a biome characterized by, relating to, or requiring only a small amount of moisture,merriam-webster.com merriam-webster dictionary definition of xeric usually defined as less than 250&nbsp;mm of annual precipitation. it is the largest terrestrial biome, covering 19% of the earth's land surface area. they may be further characterized as hyperxerÃ³fila (very dry) and hypoxerÃ³fila (less dry). ==character of the biome==   ===biodiversity=== deserts and xeric shrublands may have extraordinarily rich floras with very high alpha and beta diversity; reptile faunas may also be very diverse; local endemism may be quite pronounced in some regions. ===minimum resources=== many species track seasonally variable and patchy resources and require large natural landscapes to persist; water sources and riparian habitats are critical for the persistence of many species. ===poor soils=== because biomass productivity is low, the litter layer is almost nonexistent and organic content of surface soil layers is very low. finally, evaporation tends to concentrate salts at the soil surface. ===sensitivity to disturbance=== highly sensitive to grazing, soil disturbance, burning, plowing, and other cover alteration; restoration potential can be very low and regeneration very slow; exotic species may be a serious problem. ==desertification== the conversion of productive drylands to desert conditions is known as desertification, and can occur from a variety of causes. one factor is human intervention in imposing intensive agricultural tillage or overgrazingc.michael hogan. 2009. overgrazing. encyclopedia of earth. sidney draggan, topic ed.; cutler j. cleveland, ed., national council for science and the environment, washington dc in areas that cannot support such exploitation. climatic shifts such as global warming or the milankovitch cycle (which drives glacials and interglacials) also affect the pattern of deserts on earth. ==desert and xeric shrublands ecoregions==        ==see also== *arid forest research institute (afri) *xeriscaping- gardening or landscaping in xeric environments * xerophytes- plants adapted to xeric environments *shrub-steppe *temperate grasslands, savannas, and shrublands *[[sag
Deserts_and_xeric_shrublands Flora_of_the_California_desert_regions North_American_desert_flora Terrestrial_biomes