Biological change of western Saudi Arabia: Alien plants diversity and their relationship with edaphic variables

Objectives: In the current study, the diversity of invasive alien species in the diverse region of western Saudi Arabia and their existence in different habitats were examined. Methods: A total of 58 stands in different habitats (i.e., mountains, protected areas, wadis, coastal areas, farmlands, and ruderal areas) along the western region of Saudi Arabia were examined to record the different native and alien plant species in the study area. Results: The results revealed the existence of 146 plant species including 52 alien species. Alien plant species were characterized as casual (4 species), naturalized (45 species), and invasive (3 species). Invasive and casual species were mainly trees and shrubs while naturalized species were mainly annual herbs and subshrubs. Moreover, most of the invasive and casual alien species belonged to the American region while the naturalized species were mainly from the Saharo-Arabian region. Opuntia dillenii (Ker Gawl.) Haw. and Prosopis juliflora (Sw.) DC. showed the highest frequencies among the identified alien plant species as each was found in 4 out of the 6 examined habitats. Interestingly, P. juliflora was the only invasive species in the ruderal areas. O. dillenii dominated mountain habitats, protected areas, and farmlands. Canonical correspondence analysis showed that the distribution of O. dillenii was correlated with soil pH and organic matter content in the soil, while the distribution of P. juliflora showed a correlation with the soil contents of K, Ca, and Mn. Conclusions: The results of the current study could help in enhancing the strategic conservation of plants and controlling the spread of these invasive alien species in Saudi Arabia