Abstract.Moringa peregrina which is one of the most valuable and economically important medicinal species in the Egyptian desert has become one of the most endangered trees due to unmanaged grazing and over-collection. The present study aims to provide ecological assessment of the species and to investigate whether progeny from the remnant fragmented populations show reduced fitness. Sixteen sites containing a total of 197 trees were sampled upon survey of Wadis in South Sinai, where vegetation parameters and associated species were recorded. Variation in edaphic factors, phenotypic traits, germination, and early life-history fitness were assessed and analyzed. The results indicated that M. peregrina has narrow distribution and grows on cliffs and at the base of hills (300 -800 m a.s.l.) with very rugged topography. Almost all the reproductive trees grow on south facing slopes and crevices of metamorphic rocks. The study clearly showed that the studied populations have very low early stage fitness estimated as an index of maternally affected life-history characters. The study suggested that the deteriorated environmental circumstances have affected negatively the fitness of maternal plants in small populations and the performance of their offspring. It concluded that direct protection is urgently needed to stop further deterioration of the populations and to improve their number and size.

Acacia trees in Sinai desert are suffering population decline. This study aims to explore this assumption and to determine the effects of grazing and urbanization on size structure of Acacia tortilis subsp. raddiana along a gradient of water availability in Wadi Feiran basin, South Sinai, Egypt. Size structure of 289 Acacia trees in thirteen isolated populations was analysed. Catchment area and lineament density as water availability indicators were calculated. Effects of grazing and urbanization on Acacia populations were evaluated. A strong positive correlation was recognized between tree height, crown diameter and trunk circumference. Acacia tree density and crown diameter are positively correlated with water availability indicators. Population structure of A. tortilis is characterized by absence of juveniles, clear reduction in numbers of small and large categories and increasing in medium categories. This pattern indicates very low recruitment and high mortality of small and large trees. The variation in water availability may have considerable effects on the structure of A. tortilis. Overgrazing, cutting and urbanization are the main causes of population decline of Acacia in Sinai desert. In addition, drought conditions and bruchid seed beetles aggravate the anthropogenic effect on recruitment of Acacia in South Sinai.

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