Abstract
Arid and semiarid regions are characterized by a unique floristic composition and structural diversity of their plant communities. The goal of the present study is to investigate the effect of physical and chemical properties of soil on these characteristics of the arid region of Tabuk in Saudi Arabia. With beta diversity, the variability of a plant species composition has been studied at four sites (Alwaz, Alqan, Sharma, and Zetah) of the region. Two taxonomic diversity indices, average taxonomic distinctness (Delta+) and variation in taxonomic distinctness (Lambda+), have been calculated, and the effect of the environmental situation and limitations of environmental conditions on these indices have been determined. The study represents the first stage of a study intended to evaluate the taxonomic diversity of plant communities of the arid region of the Arabian Peninsula and its connection with soil properties. According to the results, anthropogenic factors (woodcutting, pasture, and urbanization) significantly influence the floristic diversity. It is proposed that urgent strategies of nature conservation be developed to protect plant habitats and prevent their destructive changes.