Vegetation-Soil Relationships in Wadi El-Rayan Protected Area, Western Desert, Egypt

The present study provides an analysis of the soil and vegetation composition at 10 sites in Wadi El Rayan Protected Area and concentrates on the environmental factors that affect plant species distribution. A total of 17 vascular plant species belonging to 13 botanical families was recorded. Poaceae, Chenopodiaceae, and Zygophyllaceae were the largest families identified. Chorological analysis revealed that 47% of the studied species are Pluri-regional, 41% are Bi-regional and 12% are Mono- regional. The recorded species extend their distribution all over the Saharo-Arabian (33%) followed by Irano- Turanian (24%), Mediterranean (22%), Palaeotropical (8%), Sudano-Zambezian (5%), Neotropical (5%), and Euro- Siberian (3%). The life-form spectrum revealed that the phanerophytes (35%) and geophytes helophytes (23%) are the most frequent, followed by chamaephytes (18%), therophytes (12%), hemicryptophytes (6%), and helophytes (6%). The dominant species were Phragmites australis, Tamarix nilotica and Zygophyllum album; while the co-dominant species were Juncus rigidus, Nitraria retusa, Alhagi graecorum, Typha domingensis, Zygophyllum coccineum and Eucalyptus camaldulensis. Variation in species diversity among different locations were evident, the Northeast of the Lower Lake(9 species), followed by the Southwest of the Lower Lake and the Northeast of the Upper Lake(6 species each) showed highest species richness, while the Southeast of the Lower Lake showed the lowest recorded species richness (one species). Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) Ordination techniques were used to examine the relationship between the vegetation and soil parameters; pH, electric conductivity, CaCO3, organic matter and relative concentrations of cations.CCA analysis showed positive correlations of species and sites along the most important ecological gradients. Both ordination techniques clearly indicated the importance of these ecological factors on the distribution of the vegetation pattern in the area.