SPECIES DIVERSITY AND FLORISTIC COMPOSITION OF RAWDHAT ABALWOROOD VEGETATION IN AL-ASYAH, ALQASSIM REGION, SAUDI ARABIA

. Rawdhat Abalworood in Al-Qassim region of Saudi Arabia is one of the most important rawdhats of this area. The present study provides insight of vegetation types, life forms, as well as floristic categories and species distribution, highlighting the ecological factors that influence species distribution. A total of 44 species representing 19 families of vascular plants were recorded. The dominating groups were Asteraceae and Brassicaceae, and the dominant life forms were therophytes and chamaephytes, displaying a typical desert life-form range. Two of the eighteen studied sites had the maximum species richness value of 15 species per plot. Five of the 18 sites studied had the lowest species richness assessing of 10 species per plot. The most frequent life form classes observed in Rawdhat Abalworood, Al-Asyah, Al-Qassim region were Therophytes (Th) and Chamaephytes (Ch), with 65.91% and 15.91%, respectively. Chorological analysis exhibited Saharo-Sindian (SA-SI) and Irano-Turanian-Saharo-Sindian (IR-TR+SA-SI) represented by 20.45% and 18.18, respectively. Chronologically, surveyed plant species were recognized into three categories; mono regional, bi regional, and pluri regional. The three chorological categories were represented by 31.81%, 50.0%, and 18.18%; respectively. Species diversity in terms of Margalef’s diversity index ( Figure 6A ) ranged between 1.6 to 2.6 with an average of 2.1 to 0.3, Shannon-Weiner diversity index ( Figure 6D ) showed close diversity levels as Margalef’s and ranged between 1.6 to 2.4 with an average of 2.1. Using CCA multivariate analysis effect of 6 environmental factors is distinguished upon vegetation. The CCA ordination revealed that the separation of Vegetation group III along the axis was influenced by Silt, WHC, OM, OC, and Clay, whereas VG II was substantially related to sand%.