Environment and vegetation in the montane Saint Catherine area, south Sinai, Egypt

The main aim of this study was to elucidate the complex inter-relations between elevation, edaphic features, topography, prevailing wind speed and vegetation distribution on Saint Catherine mountains. Vegetation sampling was carried out at 37 stands distributed on five main mountains, and the cover percent of each species was recorded in five plots (5 × 5 m) for each stand. Basic environmental information included elevation, slope degree, exposure, soil texture, nature of soil surface and speed of wind. Analysis of data involved two steps: first the vegetation matrix was classified by TWINSPAN producing six main communities: (1)Tanacetum santolinoides, (2)Artemisia inculta, (3)Artemisia inculta–Atraphaxis spinosa, (4)Artemisia inculta–Lycium shawii, (5)Artemisia inculta–Fagonia mollis, and (6)Artemisia inculta–Achillea fragrantissima. The data were summarized in two vectors of ordination scores produced by detrended correspondence analysis (DECORANA) and canonical correspondence analysis (CANOCO). The second step involved relating the ordination scores to environmental parameters by correlation analysis. Classification analysis clarified the diversity of plant communities and related them to the environmental variations fromFagonia mollison the driest and lowest elevation stands toTanacetum santolinoidesandArtemisia incultacommunities on wet and windy sites at high elevations. The distribution of plants is largely determined by a moisture gradient which is controlled by elevation, slope degree, soil texture (fine sand and coarse sand fractions), and the speed of winter and summer wind, as well as the nature of the soil surface. The nature of the soil surface in the form of boulders and stones, and cobbles and surface gravel is one of the most important factors controlling moisture availability and subsequently the distribution of plant communities in the mountains.