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Soil phosphorus (P) is one of the most important but least understood nutrients supporting productivity in terrestrial ecosystems. This study explored the relative importance of plant species richness or composition in the association with concentrations of different soil P forms in an oligotrophic grassland desert scrub system in the central region of the Chihuahuan Desert (Mexico). Our results suggest that species identity, rather than richness, is more related to pools of soil P in different forms in the studied system. However, plant species richness also appears to be related to soil P patterns when analyzed alone. Differences in Allenrolfea occidentalis coverage are associated with differences of total P pool in grassland plots between 60.4 and 110.2 mg/kg of dry soil. In desert scrub, Nerisyrenia camporum coverage is associated with total P between 207.2 and 243.8 mg/kg of dry soil. Coverage of Jatropha dioica is associated with soluble + labile P pool between 29.7 and 22.6 mg/kg of dry soil; and Larrea tridentate coverage is associated with soil organic P pool between 3.1 and 18.0 mg/1