Ecology of inland sand dunes "nafuds" as a hyper-arid habitat, Saudi Arabia: Floristic and plant associations diversity.

Sand seas of Saudi Arabia cover about one-third of the Arabian Peninsula and are still poorly explored in scientific literature. This study aimed to address the floristic structure and association diversity of the inland sand seas in central Saudi Arabia after 20 years of protection. Twenty-three relevés were selected in Nafud Al-Urayq reserve to cover different sandy dune variations. These relevés are subjected to floristic and multivariate analysis of classification with TWINSPAN and ordination with DECORANA & CANOCO techniques. One hundred thirty-five species belonging to 108 genera in 37 families have been recorded. Annual and perennial species are equally represented. Four vegetation groups (i.e., plant associations) are identified as the following: VG I (--), VG II (-), VG III (--), and VG IV (-). The association of VG I inhabited in the wadi and non-dune or shallow sand habitat had the high species diversity indices (i.e., total species, species richness, species evenness and Shannon index). In contrast, the association of VG II inhabited hyper-arid and salinized habitat and had low species diversity indices. These associations are discussed and illustrated in accordance with competition and adaptation. The advantages of inland sand dune vegetation therefore apply specifically to habitat management and the conservation of plants. These studies extend the advantages of succession of sand dunes and show that rising vegetative diversity is consistent with the combat of desertification.