Ecological study at Wadi Al-Ammaria in El-Riyadh City--Saudi Arabia.

INTRODUCTION

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).

STUDY AREA

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.

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RESULTS

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.

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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.

DISCUSSION

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.

CONCLUSION

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.

REFERENCES

(1.) Allen,S.E.; Grimshaw, H.M.; Parkinson, J.H. and Quarmby,C. (1974). Chemical analysis of ecological materials. Oxford, Blackwell Scientific Publication.

(2.) Al-Farraj, M.M.; Al-Farhan, A. and Al-Yemeni, M. (1997). Ecological studies on rawdhat system in Saudi Arabia, I. rawdhat Khorim. Pakistan Journal of botany 29 (1): 75-88.

(3.) Al-Hinai, K.G. 1989. Evaluation of remote sensing data for sand studies in Saudi Arabia, Workshop on desert studies in the Kingdom of Saudi Arabia: Scopes and concerns.

(4.) Al-Nafea, A.H. 2004. Botanical Geography of Saudi Arabia. King Fahd National Library, El-Riyadh, Saudi Arabia.

(5.) Al-Yameni, M.N. 1997. Growth response of Vigna ambacensis L. seedling to the interaction between nitrogen source and salt stress. Pakistan Journal of Botany 29 (2): 323-330.

(6.) Al-Yameni, M.N. 1998. The effect of drought on growth and dry matter allocation in seedlings of Vigna ambacensis L. J. King Saud Univ. Sci. 10 (1): 41-51.

(7.) Al-Yameni, M.N. 2000. Ecological studies of sand dune vegetation in Al-Kharj region, Saudi Arabia. Saudi Journal of Biological Sciences 7 (1): 64-87.

(8.) Al-Yameni, M.N. 2001. Ecology of some plant communities in Wadi Al-Ammaria, Riyadh, Saudi Arabia. Saudi Journal of Biological Sciences 8 (2): 145-165.

(9.) Al-Yameni, M.N. and Zayed, K.M. 1999. Ecology of some plant communities along Riyadh Al-Thumamah road, Saudi Arabia. Saudi J. Biol. Sci. 6 (1): 9-26.

(10.) Al-Yameni, M.N. and Al- Farraj, M.M. 1995. The seed bank of desert soil in central Saudi Arabia. Pakistan Journal of Botany 27 (2): 309-319.

(11.) Batanouny, K.H. 1987. Current knowledge of plant ecology in Arab Gulf Countries. Catena 14: 291-316.

(12.) Chaudhary, S.A. 1999. Grasses of Saudi Arabia. Riyadh, National Agriculture and Water Research Center, Ministry of Agriculture and Water, Saudi Arabia : 465 pp.

(13.) El-Ghanem, W.M. 2006. Factors affecting the Vegetation in Saudi Arabia. Bio-Science Research Bulletin. Vol.22(No.1)(Under Press)

(14.) El-Sheik, A.M. and Yousef, M.M. 1981. Halophytic and xerophytic vegetation near Al-Kharj springs. J. Coll. Sci., Riyadh Univ. 12: 5-21.

(15.) Shaltout, K.H. and Mady, M. 1996. Analysis of raudhas vegetation in Central Saudi Arabia. Biodivers. Conserv. 5: 27-36.

(16.) Shaltout, K.H.; El-Halawany, E.F. and El-Garawany, M.M. 1997. Coastal lowland vegetation of eastern Saudi Arabia. Biodivers. Conserv. 6: 1027-1040.

(17.) Taia, W.K. and El-Ghanem, W.M. 2001. City vegetation analysis of three habitats at El-Riyadh. Bull. Pure and Appl. Sci. 20B (1): 53-65.

(18.) Zayed, K.M. and El-Karemi, Z.A.R. 1989. Vegetation between Taif and El-Shafa highland, (Asir mountains), Saudi Arabis. Feddes Repertorium 100 (11-R): 661-672.

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