Vegetation composition and floristical diversity in date palm orchards of Central Saudi Arabia

The present study deals with the floristical composition of date palm orchards in Central Saudi Arabia (Al-Qassim Area). Fifty-five species of vascular plants were recorded, including 29 perennials and 26 annuals. Fifteen date palm orchards (stands) in each of five studied locations were investigated. Fifteen soil parameters were used to assess the relationship between species distribution and their controlling soil factors. Three main vegetation groups (A, B and C) were identified, and their characteristic species were recognised. These groups were separated along the first two axes of the principal component analysis (PCA). None of the measured soil variables showed significant difference between the identified vegetation groups. The first RDA axis can be defined as coarse sand-silt gradient, while the second axis, can be defined as potassium-coarse-sand gradient.