干旱区生态环境知识资源中心

The floristic diversity and vegetation-environment relations in the southern part of the Eastern Desert, between 26 degrees 45’N and 24 degrees 1’N and between 32 degrees 45’E and 35 degrees 00’E and covering a total area of about 54,500 km(2), were investigated. For this purpose, 142 georeferenced stands distributed in four transects were selected: 22 from Qena-Safaga road (T1), 28 from Idfu-Marsa Alam road (T2), 46 from Aswan-Kharit-Gimal (T3), and 46 from Red Sea Coastal Plain (T4). Altogether, 94 species belonging to 33 families were recorded, and the species richness (SR) varied from one transect to another: 46, 35, 52, and 46 in T1, T2, T3, and T4, respectively. Soil samples were collected from each stand, and the soil texture, soil moisture content, organic matter (OM), electric conductivity (EC), total soluble salts (TSS), pH, and major ions (Na+, K+, Ca+2, Mg+2, C-l-, SO4-2, and HCO3-) were determined. The soil-vegetation relationships were assessed by both detrended correspondence analysis and canonical correspondence analysis. Both species diversity measurements (SR and H’) exhibited significant differences among the separated vegetation groups within each transect. Classification of the vegetation resulted in 6, 7, 4, and 6 vegetation groups for T1, T2, T3, and T4, respectively. Canonical correspondence analysis showed well the relative positions of species and sites along the most important ecological gradients. The segregation of these groups along the first two axes of the biplot demonstrated that soil texture, moisture content, salinity, sulfates, and organic matter contents were highly correlated with the distribution of species.