Species Diversity and Distribution along the Area Jeddah-Rabigh, Saudi Arabia

Abstract. The study assesses the plant communities and environmentalfactors that govern species diversity (alpha and beta diversity)and distribution in the area extending from Jeddah to Rabigh at theRed Sea coast. Sixty-four plant species were recorded (43 perennialsand 21 annuals). Zygophyllum coccineum, Panicum turgidum and Cyperusconglomeratus of perennials and Zygophyllum simplex of annualsattained high presence percentages in most of the selectedstands. Four vegetation groups with their sub-groups, which arepresent in the six different habitat types in the study area, were recognizedby applying NTSYS-PC classification technique. Group Awas divided into two subgroups, A1 that was indicated by Zygophyllumcoccineum and Suaeda pruinosa and subgroup A2 that wasindicated by Zygophyllum album and Acacia seyal. Group B was alsodivided into two subgroups, B1 that was indicated by Limonium axillareand Cyperus conglomeratus and subgroup B2 that was indicatedby Acacia tortilis and Heliotropium ramosissimum. Group C was indicatedby Indigofera spinosa and Panicum turgidum and group Dwas indicated by Acacia tortilis and Acacia ehrenbergiana. Soil texture,water holding capacity, Na, Ca and SO4 contents were the bestpredictor variables for species distribution in the study area. The resultsof beta diversity indicated that the study area must be dividedinto six different habitats. Low species richness was associated withmore saline conditions and mobile dunes in the study area.