Environment and vegetation of Randonia africana: an endangered desert plant in Egypt

Randonia africana Coss. (Resedaceae) is a perennial endangered vascular plant species in Egypt. It inhabits the sandy plains along Mersa Matruh-Siwa Oasis road crossing the Western Desert of Egypt, where it represents the easternmost limit of distribution in North Africa. The vegetation associates within each of the five known population sites of R. africana were studied, and their edaphic correlates were analysed. Classification and ordination techniques were employed to the importance values of the 29 recorded species in 25 stands. Application of TWINSPAN classified the floristic data into five vegetation groups, and separated along detrended correspondence analysis axes 1 and 2. Group E was the most diversified among the other vegetation groups, while monotypic stands of R. africana (group B) was the least. Detrended canonical correspondence analysis (DCCA) indicated that the distribution of R. africana and its associates was mainly controlled by soil salinity, percentages of surface sediments of different size classes, calcareous deposits, and organic matter. [PUBLICATION ABSTRACT]