Moisture and Salinity Drive the Vegetation Composition of Wadi Hargan, Riyadh, Saudi Arabia

Abstract

Wetlands are represented in Saudi Arabia in the form of mangrove, sabkha, and wadi (valleys) systems, and these habitats are considered as a sanctuary for biodiversity. The present study aimed to identify different vegetation groups in a wetland site in Wadi Hargan near Alqurainah, Riyadh, Saudi Arabia, and to relate different plant communities and plant diversity to soil moisture, salinity, and other soil properties. Floristic analysis and vegetation structure were investigated within 15 stands along the wadi and were subjected to correlation analysis with soil factors via multivariate analysis. The floristic survey revealed the presence of 111 plant species belonging to 39 families. The most represented families were Asteraceae, Poaceae, Brassicaceae, Caryophyllaceae, and Papilionaceae, which accounted for the largest proportion (55.4%) of the total species. The therophytes were the dominant life form, where they were represented by 46.9% of the total number of species. The application of cluster analysis (TWINSPAN) to the importance value of each species based on the relative cover and density led to the recognition of four plant communities: (A) Phragmites australis—Tamarix nilotica community, (B) Zygophyllum coccineum—Acacia gerrardii community, (C) Lycium shawii—Zygophyllum coccineum community, and (D) Rhazya stricta community. The soil analysis and correlation test revealed significant variations in the content of salinity, moisture, CO3, Cl, SO4, Ca, Mg, and Na among the plant communities. It can be concluded that soil moisture and salinity factors were the fundamental driving forces for plant community structure in the studied wadi. The wadi was moderately grazed, mainly by camels; thereby, the invasive plant Rhazya stricta dominated the central region of the wadi. Also, human interference was observed at the end of the wadi, where some weeds sprouted such as Malva parviflora. The presence of those two rare wetland species, Adiantum capillus-veneris and Ficus salicifolia, in the study area, showed the unique properties of the studied wadi and necessitate an urgent biodiversity conservation action to protect its natural vegetation from overgrazing and human interference.

Vegetation Composition of the Halophytic Grass Aeluropus lagopoides Communities within Coastal and Inland Sabkhas of Saudi Arabia

“…The perennial halophytes can tolerate high salt content in soil [ 33 ]. The predominance of Poaceae, Chenopodiaceae, and Mimosaceae in the studied habitats was in harmony with other previous studies in different saline habitats [ 25 , 34 ]. On the other hand, most of the recorded species belong to the Saharo-Arabian element.…”

“…Saudi Arabia is located within an arid and semi-arid zone. It is distinguished by its different ecosystems, including mountains, meadows, valleys, rocky and sandy deserts, and salt marshes [ 11 , 25 ]. Among salt marsh ecosystems, there are inland salt marshes and saline coastal habitats, called sabkhas.…”

“…In Saudi Arabia, A. lagopoides grows in various coastal and inland sabkhas [ 23 , 24 ]. It is restricted in the form of specialized vegetation patches in the Wadi Hargan, Riyadh, salt marsh sabkha of the Qaseem and Jouf, and coastal zones of the Salwa and Jizan regions [ 25 , 26 ]. It is of economic importance, where it is utilized as fodder in arid areas, used to stabilize sand dunes [ 27 ], and can be used for landscaping of the urban areas [ 28 ].…”

“…Knowledge of the ecological distribution of key species is the primary characteristic of its conservation strategy in its ecosystem [ 29 ]. Apart from the establishment and maintenance of the protected area, baseline information about the key species, vis a vis the associated species, edaphic factors of the habitats, environmental variation, anthropogenic activities of the regions, are crucial [ 25 , 30 ]. This ecogeographical survey is considered central to all the conservation issues and a key requisite in the development of the conservation strategy [ 31 , 32 ].…”

Arbuscular Mycorrhizal Fungi Isolated from Highly Saline “Sabkha Habitat” Soil Alleviated the NaCl-Induced Stress and Improved Lasiurus scindicus Henr. Growth

“…Unique saline-beds or saline-plains known as Sabkhas are widely found in Saudi Arabia's dry and semi-arid terrain [1,2], and they range from a few hectares to hundreds of square kilometers. Sabkhas are generally scarce of vegetation and mainly inhabit saltresistant halophytic species, derived through the variation in moisture and salinity [3,4]. Soil salinity (ECe > 4 dSm −1 ) is considered one of the most worrying abiotic stresses to plants, especially in arid and semi-arid regions [5].…”