VII.A. Consolidated rock sparse vegetation. Pavement with sparse vascular vegetation VII.A.2.N.a.010. This alliance contains one community characterized by large expanses of exposed granite surfaces, with scattered soil-filled depressions, crevices, gravel areas, and shallow pools.
Vegetative cover is sparse and limited to areas where shallow sand or gravel accumulate.
Typical species include Sedum nuttallianum , Plantago wrightiana , Talinum parviflorum , Helenium amarum , Campanula reverchonii , Aphanostephus skirrhobasis , Hypericum gentianoides . Areas with deeper soils are dominated by Schizachyrium scoparium occurring with other grasses such as Bouteloua hirsuta , Bouteloua curtipendula , and Aristida purpurea . Bare rock is occupied by scattered patches of crustose and foliose lichens, mosses, and several ferns and fern allies including Selaginella peruviana, Selaginella arenicola ssp. Narrow, shallow crevices harbor species tolerant of the most xeric conditions including Echinocereus reichenbachii , Eriogonum tenellum , and Opuntia leptocaulis . This community occurs on gently sloping, exposed massifs of late Precambrian granite in Texas and Oklahoma.