Plant communities and their environmental drivers on an arid mountain, Gebel Elba, Egypt

By Maged M. Abutaha, Ahmed A. El-Khouly, Norbert Jürgens & Jens Oldeland

The arid mountain Gebel Elba represents the core of the most diverse and most extensive protected area in Egypt; Gebel Elba National Park. Although the climate of the open desert is hyper-arid, leading to a scattered woodland, a mist oasis can be found on the mountain supporting dense and vital vegetation. The vegetation of Gebel Elba shows an altitudinal zonation comparable to the neighbouring highlands of East Africa and the south-western Arabian Peninsula. The lower altitudes are dominated by Vachellia tortilis woodland (synonym:  Acacia tortilis woodland) while figs (Ficus salicifolia and F. palmata) and olive trees (Olea europaea subsp. cuspidata) are recorded at higher elevations.

Gebel Elba has been overlooked in most global biodiversity assessments. Only a few studies focused on the floristic composition and described the vegetation zonation, while the phytosociological classification of the vegetation was still lacking. In our study, we classified the plant communities of Gebel Elba and identified the main environmental drivers controlling their distribution. Further, we studied the plant diversity along the altitudinal gradient from the open desert to the mountain drainage systems at higher elevations.

We focused on the vegetation of wadi (valley) systems on the northern slopes of Gebel Elba. Our sampled vegetation plots were distributed in Wadi Yahmib and its main tributaries, the wadis Marafai, Acow and Kansisrob. We found that the mountain wadis are more diverse than the open desert plains due to big climatic differences. We identified seven Afrotropical plant communities from which two were dominated by evergreen trees (figs and olive) and the others by deciduous trees (e.g., Vachellia tortilis and Balanites aegyptiaca). Altitude, soil quality and topography were the most important environmental factors shaping vegetation structure and distribution. Furthermore, we identified an ecotone area at mid-altitude (450-550 m a.s.l.) between the deciduous Vachellia woodland and evergreen Olea woodland. This study is the first which explores the plant communities, their plant diversity and controlling environmental factors of the unique arid mountain Gebel Elba in Egypt.

This is a plain language summary for the paper of Abutaha et al. published in the Vegetation Classification and Survey (https://doi.org/10.3897/VCS/2020/38644). This post was prepared by Maged Abutaha & Jens Oldeland.