Ecological study at Wadi Al-Ammaria in El-Riyadh City--Saudi Arabia.
Saudi Arabia is one from the biggest countries in the world. It occupied about 4/5th of the Arabian Peninsula with great variations in climates, elevations, soil and vegetative characters. From this great area of the kingdom, sand dunes occupy about 1/4 of it (Al-Hinai, 1989). For that many ecological works have been done to elucidate these variations. From the recent works are those of Al-Yemeni and Al-Farraj (1995); Al-Farraj et al. (1997); Shaltout et al.(1997), Al-Yemeni (1997, 1998, 2000& 2001); Chaudhary (1999); Al-Yemeni and Zayed (1999); Taia and El-Ghanem (2001); and El-Ghanem (2006). All of these works, beside many others, studied the vegetations in deferent parts in Saudi Arabia and observed that climatic and edaphic factors have the principle effects on the type of vegetation communities and distribution in the country.
Land topography in Saudi Arabia has lot of variations. There are mountains, hills, plateaus, plains, depressions and wades. These land variations greatly affected both climates and vegetations; meanwhile the soil is poor and can be considered Entisols, Inceptisols or Aridisols (Al-Nafea (2004). Thus, variations in speciation in the wades are due to differences in soil characters and type.
Wade Al-Ammaria is a branch of wade Hanifa which is allocated 25 Km to the north west of El-Riyadh city in central Saudi Arabia (Fig.1). The wade is about 22 Km in length with variable width. It has variable soil characters and accordingly the vegetation is deferent along the wade. These variations were the purpose of studying the ecological variations as well as plant speciation in it.
MATERIALS AND METHODS
This study carried out from Nov. 2005 till April 2006. Monthly visit to the wade has been carried to record the plant species and distinguish the different plant communities which are dominant along the wade. To give accurate description of the vegetation, twenty stop have been done, every 1 Km and soil has been described at every change as well as the type of vegetation. Records of temperature and rainfall on El-Riyadh city throughout the last ten years (1996-2005) have been taken from Meteorological and Environmental Protection Administration. Means of both degree of temperatures and rainfall have been calculated to draw relationship between them. Vegetation analyses were done by making random quadrates at each stop to calculate the Importance Value (I.V.) of each species.
Three replicates of soil samples were collected from 10-15 cm. depth from each defferent appearance of soil to determine their physical and chemical characters according to (methods of Allen et al. (1974).
The study area is along the wade that is extended about 22 km with a width about 300 meters and become wider in some parts and reaches 1Km. For that the vegetation and soil characters along the wade has been studied, in order to recognize their variations.
[FIGURE 1 OMITTED]
The results are illustrated and summarized in tables 1 and 2 and figs. 2-8. From Fig.2, we can notice that El-Riyadh city is a dry area with scanty rainfall and high temperatures most of the year. The mean temperature in the summer period, reach 36[degrees]C. While the annual monthly mean of the rainfall during the winter period, around 10.8 mm. This arid climate greatly affected the vegetation in the studied area.
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From table 1 and Figs.3-8, we can find that the soil physical characters change along the wade. At the beginning of the wade, the soil is covered by calcareous layer and its color is whitish yellow (Fig.3). After 1 Km, the soil starts to be sandy and yellow (Figs.4-8). Generally, along the wade the soil is alkaline and poor with very low organic matter, carbonates and salt contents.
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The vegetation along the wade can be described by being poor with low speciation and cover. In spite of that, we can recognize 33 species and seven community types along the wade. These types are dominated by perennial xerophytes throughout the studied period.
[FIGURE 8 OMITTED]
The seven community types are as follows:-
Acacia ehrenbergiana type 1-
This community is dominated by Acacia species and accompanied with Alhagi mannifera, Alhagi maurorum, Hyoscymus muticus and Phaeopappus scoparius. These species are the most effective ones in that community type, since there are others but few. This type present in the beginning of the wade.
Echinops husoni type 2-
This community is dominated by Echinops husoni and accompanied with Basia eriophora, Crotalaria aculeate, Alhagi maurorum and Zilla spinosa. This species dominated after about one Km from the beginning of the wade.
Salsola imbricate type 3-
In this type Salsola species dominated with Echinops husoni and accompanied with Alhagi mannifera, Alhagi maurorum, Convolovulus lanatus and Heliotropium species. This community found after 2-3 Km from the beginning.
Alhagi maurorum type 4-
This community type is distributed throughout the wade which is dominated by Alhagi maurorum and accompanied with Rhynchosia minima, Calotropis procera, Zilla spinosa and Pennisetum divisum.
Pennisetum divisum type 5-
This type is distributed along the sandy parts of the wade, in which Pennisetum divisum is dominated and accompanied by few species such as Cyperus conglomerates and Tephrosia uniflora.
Rhazia srticta type 6-
Which is present in the mid of the wade together with Aerva javanica, Hyoscymus muticus and Phaeopappus scoparius.
Haloxylon salicornicum type 7-
This community type is found along the wade distributed apart from the other communities with the dominance of Haloxylon salicornicum with Salsola imbricate.
The study of the ecological features and vegetation types in the different topographical features has been carried out by many ecologists. El-Sheikh and Yousef (1981) attribute the scanty vegetation in El-Kharj to the combined effect of both the atmospheric and edaphic factors. While Shaltout and Mady (1996) suggested that human impacts plays an important role in the type of vegetation. Meanwhile, Al-Yemeni (2000) referred the differences in the structures of the vegetation to climatic aridity, topography, edaphic characters and human impacts.Taia and El-Ghanem (2001) studied the vegetation in three habitats in El-Riyadh city, from them is wade Hanifa, and they found that the main factors affecting the vegetation are both amount of available water and edaphic factors. While Shaltout et al (1997) found that both plant communities and environmental factors govern species richness and distribution.
In this study we recorded seven community types along the wade. These communities are dominated by one species with few associates. All of them are xerophytic species and those which can grow in disturbed habitats like Salsola imbricate, Rhazya stricta, Haloxylon salicornicum, Calotropis procera, Alhagi sp. and Zilla spinosa. These species beside the rest are adapted to live in the desert, disturbed and poor soils. Thus, the presence of these species reflect the environmental stress in this open desert, inspite of being a wade but it still has the characters of sandy deserts. The presence of Acacia community type occurs in the low-lying localities which receives more water, while Alhagi community is mainly in the beginning of the wade where the compact calcareous soil. Haloxylon, Salsoila and Rhazya communities present along the wade where is the soil is sandy and sand dunes present.
These community types coordinate with those obtained by Al-Yemeni (2000), but he recognized eight community types in wade Al-Ammaria. It is, also in accordance with the results obtained by Batanouny (1987) and Zayed and El-Karemi (1989) as they found that Acacia species dominates only in sandy soil and the depressions where there is plenty of water in both Asir and the northern and eastern parts of Saudi Arabia.
In conclusion, we can describe the study area by being arid and the type of vegetation by being scanty xerophytes with low speciation throughout the year. Meanwhile the wade is under severe grazing activity which may affect species richness, thus we have to advice peoples to regulate grazing to improve the state of the plants and enrich speciation.
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Wafaa Mohammed El-Ghanem
College of Education for Girls--Scientific Section--El-Malas El-Riyadh--Saudi Arabia
Table 1: Soil Characters along Wade Al-Ammaria Chemical composition [right arrow] Contents pH EC CO3 [down arrow] Distant Texture [micro]mohs/cm % Beginning Calcareous 7.85 0.1642 2.635 After 1Km Sandy 7.9 0.1841 0.412 After 3Km Sandy 8.2 0.2011 0.237 After 5Km Sandy 8.62 0.1782 0.218 After 10Km Sandy 8.42 0.1523 0.221 Chemical composition [right arrow] Contents Org.mat. Na K Cl [down arrow] Distant % Ppm Ppm % Beginning 1.324 0.325 0.641 0.019 After 1Km 1.498 0.228 0.701 0.032 After 3Km 2.011 0.139 0.698 0.035 After 5Km 0.236 0.401 0.312 0.041 After 10Km 0.169 0.522 0.298 0.029 Table 2: Species recorded and their taxonomical status No. Species Division Class Subclass 1 Cleome Spermatophyta Angiospermae Dicots. droserifolia 2 Zilla spinosa 3 Citrullus colocynthis 4 Fagonia cretica 5 Zizphus spina- christi 6 Aerva javanica 7 Bassia eriophora 8 Cornulaca monacantha 9 Haloxylon salicornicum 10 Salsola imbricata 11 Acacia ehrenbergiana 12 Acacia gerrardii 13 Acacia tortolis 14 Logonychium farctum 15 Alhagi mannifera 16 Alhagi maurorum 17 Rhynchosia minima 18 Crotalaria aculeate 19 Tephrosia uniflora 20 Rhazia stricta 21 Calotropis procera 22 Hyoscymus muticus 23 Lycium barbarum 24 Convolvulus lanatus 25 Heliotropium bacciferum 26 Heliotropium digynum 27 Heliotropium europium 28 Echinops husoni 29 Phaeopappus scoparius 30 Rhanterium epapposum 31 Panicum Monocots turgidum 32 Pennisetum divisum 33 Cyperus conglomeratus No. Species Order Family 1 Cleome Papaverales Cleomaceae droserifolia 2 Zilla spinosa Cruciferae 3 Citrullus Cucurbitales Cucurbitaceae colocynthis 4 Fagonia Geraniales Zygophyllaceae cretica 5 Zizphus spina- Rhamnales Rhamnaceae christi 6 Aerva javanica Centrospermae Amaranthaceae 7 Bassia Chenopodiaceae eriophora 8 Cornulaca monacantha 9 Haloxylon salicornicum 10 Salsola imbricata 11 Acacia Rosales Leguminosae ehrenbergiana 12 Acacia gerrardii 13 Acacia tortolis 14 Logonychium farctum 15 Alhagi mannifera 16 Alhagi maurorum 17 Rhynchosia minima 18 Crotalaria aculeate 19 Tephrosia uniflora 20 Rhazia stricta Gentianalis Apocynaceae 21 Calotropis Asclipiadaceae procera 22 Hyoscymus Tubiflorae Solanaceae muticus 23 Lycium barbarum 24 Convolvulus Convolvulacea lanatus 25 Heliotropium Boraginaceae bacciferum 26 Heliotropium digynum 27 Heliotropium europium 28 Echinops husoni Campanulales Compositae 29 Phaeopappus scoparius 30 Rhanterium epapposum 31 Panicum Graminales Graminae turgidum 32 Pennisetum divisum 33 Cyperus Cyperaceae conglomeratus
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|Author:||Ghanem, Wafaa Mohammed El-|
|Publication:||Bulletin of Pure & Applied Sciences-Botany|
|Date:||Jan 1, 2006|
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