Vegetation of Beni Bousera (northern Morocco) ultramafic soils and adjacent non-ultramafic soils in relation to edaphic factors

Vegetation and soil sampling were undertaken in 47 relevés in two different sites in Beni Bousera (northern Morocco), 32 relevés were on ultramafic sites (peridotite) and 15 were on adjacent non-ultramafic soils (mica-schist). Soil composition of exchangeable elements (nickel, calcium, magnesium, calcium : magnesium ratio, iron, copper) and physicochemical characteristics (e.g. pH, cation exchange capacity, conductivity, carbonate) were investigated and the species composition and cover were recorded. Although there was a significant difference between the two types of soil shown by Student’s t-test and principal component analysis, the ‘serpentine factor’ can be considered moderate on the basis of the observed heavy metal concentrations and of the related calcium : magnesium ratio. Correspondence and canonical analysis were used to detect the principal factors associated with gradients in species composition. This analysis showed a clear differentiation of vegetation among the plant communities. Preferential or strict serpentinophyte species were recognised, whereas no hyperaccumulator species have yet been found.