Vegetation-environment relationship and floristic diversity of Wadi Al-Sharaea, Makkah Province, Saudi Arabia

Due to their biological significance, physiographic variation, and environmental gradients, desert wadis are essential habitats for socioeconomic development. The current study aims to enrich the knowledge about the importance of Wadi Al-Sharaea, Makkah as a biodiversity hotspot for desert ecosystems in terms of floristic composition, community structure, potential economic uses of identified plants, and behaviour of the common species along soil physicochemical gradients. To collect the data, 95 stands distributed in 17 sampling sites were selected to represent the vegetation physiognomy along the wadi. During the field survey, 110 species belonging to 77 genera and 33 families were discovered with Poaceae family dominating. Therophytes were the dominant life form, and bioregional elements were the dominant chorotype. The TWINSPAN analysis resulted in nine vegetation groups (VGs), which were distinctly segregated on the two axes of DECORANA. Rhiza stricta dominated three VGs (G, H, and I) with Citrullus colocynthis, Polycarpaea repens, and Aristida funiculata, respectively, were codominant species. The Principal Component Analysis (PCA) ordination clarified that the pH, EC, TDS, Mg, and gravels had the most significant effect on the plant communities. Regarding the Pearson correlations, some plant communities were positively affected by some soil variables (e.g., pH, HCO3, K, and Cl), while others were negatively affected by other variables (e.g., EC, TDS, Ca, SO4, and Cl). The species richness varied from 1.5 species stand(-1) in Maerua crassifolia-Cynanchum radians community (VG: A) to 21.0 species stand(-1) in Citrullus colocynthis-Hypertelis cerviana (VG: B). The low species diversity in some plant communities indicated that the original vegetation was subjected to destruction, and consequently, habitat rehabilitation is urgently required.