Floristic Diversity and Vegetation of the Az Zakhnuniyah Island, Arabian Gulf, Saudi Arabia

Islands are broadly recognized as hotspots of ecology, biological and geophysical diversity with unique plant species. The present study aimed to address the floristic composition in the Az Zakhnuniyah Island along the Arabian Gulf of Saudi Arabia. A total of 21 quadrats, of 100 m(2) each were sampled, and both relative density and cover were determined. Classification (Agglomerative Hierarchical Clustering {AHC} and ordination [Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA)] were applied to identify vegetation clusters and their correlation to the underlying soil factors. Fifty plant species belonging to 21 families were recorded. Amaranthaceae (22.9%), Poaceae (12.5%), Asteraceae and Zygophyllaceae (8.33% each) were the largest represented families. Therophytes and chamaephytes were the most represented life-forms, indicating saline-desert vegetation. Most of the surveyed plant species are used for medicinal purposes and grazing. AHC and DCA allowed identifying three vegetation clusters within three distinct habitats: cluster (A): Halopeplis perfoliata-Suaeda vermiculata in wet salt-marsh habitat, cluster (B): Limonium axillare-Zygophyllum mandaville in sabkha, and cluster (C): Heliotropium bacciferum-Panicum turgidum in sand dune habitat within the island. The CCA results imply strong relationships between floristic composition and salinity measures (CaCO3, electric conductivity, Mg+2, Na+, K+, Cl- and SO4) and soil texture. The current vegetation pattern in Zakhnuniyah Island reflects a salinity gradient with variations in soil texture. Knowledge of the floristic composition and its correlation to the environmental factors within islands should guide future conservation strategy and management efforts.