Geobotanical analysis of the hillside shrublands in the potosino high plateau (south-east Chihuahuan desert, Mexico)

Abstract The mountain ranges that cross the highlands of San Luis Potosí (Chihuahuan Desert, Mexico) constitute an important refuge for different types of flora and vegetation whose distribution limits occur within these orographic and climatic ‘islands’. Shrub communities are generally included within the concepts of microphyllous, rosetophyllous and submontane scrub types. In addition, small woods of pine, oak and juniper occur towards higher zones. According to the biogeographic typology, the study area is in the Mexican Xerophytic region (Chihuahuan Province) and dominated by a Tropical Xeric bioclimate, although Tropical Desert and Tropical Pluviseasonal bioclimates also occasionally appear. The shrubs under study are included in Mesotropical and Thermotropical thermotypes. Eighty phytosociological relevés were carried out at elevations of between 1300 and 2200 m a.s.l., including a total of 208 species. Multivariate analysis enabled identification of four groups corresponding to other associations: Echinocacto platyacanthi-Agavetum lechuguillae, Ferocacto pilosi-Gochnatietum hypoleucae, Dasylirio longissimae-Heliettetum parvifoliae and Berberido trifoliolatae-Juniperetum coahuilensis. Aspects related to the structure, composition, bioclimatic affinity, dynamic-catenal position and syntaxonomic arrangement are discussed. Finally, the importance of these plant communities as refuge habitats for the flora included in some conservation categories and the threats that affect them are addressed.