Characteristics of desert vegetation along four transects in the aridenvironment of southern Egypt

摘要

The floristic diversity and vegetation-environment relations in the southern part of the Eastern Desert, between 26°45?N and 24°1?N and between 32°45?E and 35°00?E and covering a total area of about 54,500 km2, 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, Cl-, 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.