CCA ordination showing the relation between perennial species with phi coefficient > 0.25 and environmental factors represented by altitude and seven soil parameters. Variation is mostly explained by elevation (Alt), soil texture and pH. The lower left part contains species from Wadi Kansisrob. The upper part contains species of the open sandy plain, Wadi Yahmib. The right part contains evergreen species from mid to higher elevations. Eigenvalues for biplot scaling are 0.60 for axis 1 and 0.16 for axis 2 and the adjusted explained variation is 11.54%. The legend is placed at the lower right part of the figure. The diagnostic species for each community are represented by different symbols; solid symbols for communities of higher elevations and hollow symbols for communities from low to middle elevations. For species and sand fractions abbreviations see Tables 1, 3.