Abstract
Wadi Al-Noman in Mecca is one of the most important wadis. It was included among the most important water sources where the springs and wells of Zobida run and it provides drinking water for the holy places in Mecca and visitors to the Kaaba and Arafat regions. The present study provides an analysis of floristic composition, vegetation types, and structure and species distribution at 20 sites, emphasising the environmental factors that affect species distribution. A total of 126 species representing 39 families of vascular plants are recorded. Fabaceae, Poaceae, and Boraginaceae are the largest families, and therophytes and chamaephytes are the most frequent, indicating a typical desert life-form spectrum. The floristic composition of the different geomorphologic landscape units shows differences in species richness. The highest species richness value (23 species stand(-1)) is recorded in the wadi bed. The lowest species richness value (18 species stand-1) is recorded in the wadi plateau and fissures. Chorological analysis revealed that 52% of the studied species are bioregional, native to the Saharo-Arabian-Sudano-Zambezian region. After application of the TWINSPAN, DCA, and CCA programs 4 vegetation groups were identified, and they were named after the characteristic species as follows: (I) Aristolochia bracteolata-Cucumis prophetarum; (II) Calotropis procera-Acacia hamulosa-Caralluma russeliana; (III) Acacia abyssinica-Acacia hamulosa-Tephrosia desertorum; and (IV) Argemone ochroleuca-Senna italica. The associations and speciation of these Wadi Al-Noman plants demonstrate significant variation in pH, electrical conductivity, soil mineral contents, and human impact.