Anthropogenic effects on population structure ofAcacia tortilissubsp.raddianaalong a gradient of water availability in South Sinai, Egypt

Abstract

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.

Abundance, distribution, and growth characteristics of three keystone Vachellia trees in Gebel Elba National Park, south-eastern Egypt

“…In addition, soil properties, especially soil salinity, may play a role in the distribution and abundance of these taxa. Thus, the findings of the current study concerning the diversity of the three Vachellia taxa documented in these two wadis and the distribution of these taxa along a broad elevation gradient are in general agreement with similar studies conducted in south-eastern Egypt 16,17,22 , and elsewhere across the distribution of Vachellia species [12][13][14][15]23 .…”

“…(Fabaceae: Mimosoideae 8 ), which are broadly distributed around the world, are considered keystone species within the communities they reside. For example, they are considered keystone species in parts of Australia 9 , Pakistan 10 , the Kalahari Desert, Botswana 11 , Tunisia [12][13][14] , the Sinai Desert, Egypt 15,16 , and south-eastern Egypt 16,17 . As pointed out by Abdallah et al 12 , isolated trees in arid habitats, including Vachellia species., have several characteristics that contribute to their keystone status: (1) shade from their canopies prevents extreme temperature fluctuations, increases soil moisture levels, and provides shelter for wildlife, (2) they improve soil conditions through biological nitrogen fixation and litter fall by increasing soil nitrogen content, organic carbon, and water-holding capacity, (3) they increase plant and animal biodiversity as a consequence of characteristics one and two, (4) they provide a source of food for wildlife, and (5) they provide a source of fuel, fodder, and medicines for local people and their domesticated animals.…”

“…Within arid and semi-arid ecosystems across north Africa and the Arabian Peninsula, plant ecologists have focused their attention on describing the vegetation of wadis that drain to the Red Sea, with these studies focusing on keystone Vachellia species [12][13][14][15][16][17]22,23 . The present study aimed to contribute to this body of knowledge by determining the distribution, abundance, and describing the growth characteristics of three Vachellia tree taxa in wadi Khoda and wadi Rahaba, in Gebel Elba National Park, south-eastern Egypt.…”

Characterization of the wild trees and shrubs in the Egyptian flora

“…Human activities (primarily over-grazing by livestock and related disturbances) are one of the principal influences on woodland species (Oliver, 1980;Agren & Zachrisson, 1990;Skarpe, 1990;Stewart & Rose, 1990;Welden et al, 1991;Veblen, 1992;Lykke, 1998;Sakio et al, 2002;Tanaka et al, 2008). There are many examples of human destructive activities against the woody plants as mortality of Acacia trees which mainly associated with charcoal production in eastern desert of Egypt (Andersen & Krzywinski, 2007), over-grazing and over-cutting in Sinai, and aridity conditions and limited surface water availability in Sinai and Negev deserts (Shrestha et al, 2003;Abd El-Wahab et al, 2013). Local populations of Moringa peregrina are endangered due to over-cutting, and over-grazing whose effects are magnified by the contemporary prevailing extreme of drought (Zaghloul et al, 2012).…”

Traditional Uses, Pharmacological Efficacy, and Phytochemistry of Moringa peregrina (Forssk.) Fiori. —A Review

“…M. peregrina is a deciduous tree belonging to the family of Moringaceae. It is a fastest growing tree among the other Moringa species (Abd El-Wahab, 1995 ) with 3–10 m height and grayish green bark adapted to high aridity. The leaves are 30–40 cm long, alternate, obovate and deciduous.…”