Assessing the Relative Importance of Climate and Soil for Vegetation Patterns in a Semiarid Land of Central Mexico

SPECIES distribution along environmental gradients reflects the effects of several factors at different scales. The research was carried out at El Huizache Corridor, in the state of San Luis Potosi, Mexico, which is an important center of origin and diversification of cacti. The aim of the study was to assess the relative importance of climatic and edaphic factors on vegetation distribution. Using partial ordination, we analyzed in 47 sampling sites the relationships between cover values of 93 perennial plant species with 29 climatic and 19 edaphic factors. Variation partition showed that climatic variables were responsible for 14.4%, edaphic variables explained 33.6%, the interaction of both set of variables explained 11.1%; and unexplained or stochastic variation was around 41%. In addition, one vegetation type (submontane shrubland) was related to climatic factors, two (xerophytic shrublands and gypsum grassland) were related to edaphic factors, while succulent scrub was related to both set of factors.