ENVIRONMENT AND VEGETATION IN THE MONTANE SAINT-CATHERINE AREA, SOUTHSINAI, EGYPT

The main aim of this study was to elucidate the complex inter-relation s between elevation, edaphic features, topography, prevailing wind spe ed and vegetation distribution on Saint Catherine mountains. Vegetatio n sampling was carried out at 37 stands distributed on five main mount ains, and the cover percent of each species was recorded in five plots (5 x 5 m) for each stand. Basic environmental information included el evation, slope degree, exposure, soil texture, nature of soil surface and speed of wind. Analysis of data involved two steps: first the vege tation matrix was classified by TWINSPAN producing six main communitie s: (1) Tanacetum santolinoides, (2) Artemisia inculta, (3) Artemisia i nculta-Atraphaxis spinosa, (4) Artemisia inculta-Lycium shawii, (5) Ar temisia inculta-Fagonia mollis, and (6) Artemisia inculta-Achillea fra grantissima. The data were summarized in two vectors of ordination sco res produced by detrended correspondence analysis (DECORANA) and canon ical correspondence analysis (CANOCO). The second step involved relati ng the ordination scores to environmental parameters by correlation an alysis. Classification analysis clarified the diversity of plant commu nities and related them to the environmental variations from Fagonia m ollis on the driest and lowest elevation stands to Tanacetum santolino ides and Artemisia inculta communities on wet and windy sites at high elevations. The distribution of plants is largely determined by a mois ture gradient which is controlled by elevation, slope degree, soil tex ture (fine sand and coarse sand fractions), and the speed of winter an d summer wind, as well as the nature of the soil surface. The nature o f the soil surface in the form of boulders and stones, and cobbles and surface gravel is one of the most important factors controlling moist ure availability and subsequently the distribution of plant communitie s in the mountains. (C) 1995 Academic Press Limited