At higher elevations on the plateau, different types of steppe vegetation dominate depending on soil conditions, for example in the slopes and foothills of the Atlas Mountains there is a steppe dominated by Stipa tenacissima whereas Artemisia herba-alba dominates in where there are silty slopes and depressions; Lygeum spartum steppe grows in sandy soils. Where sand accumulates there is a mosaic of vegetation types including patches of Thymeleae muicrophila, Aristida pungens, Retama retam, and of tamarisks Tamarix spp. In depressions the vegetation includes a scrub consisting of the Mount Atlas mastic tree Pistacia atlantica, Ziziphus lotus, Asterichus graveolens and mallows Malva spp.