Checklist of Wadi Hassan flora, Northeastern Badia, Jordan
Feryal Kherissata, Dawud Al-Esawib     
a. Department of Biology, College of Science, Mu'tah University, P.O-7, Karak, 61710, Jordan;
b. Department of Biology, College of Science, Jordan University, P.O-13500, Amman, 11942, Jordan
Abstract: In this study, we survey the plant diversity of Wadi Hassan, which is located in the Northeastern Badia of Jordan, about 120 km east of Amman. All plant species were collected and herbarium specimens have been prepared, identified and deposited at the University of Jordan herbarium (Department of Biology, Faculty of Science). The final plant checklist includes 206 species belonging to 138 genera and 35 families. The most diverse families are Compositae (20.5%), Cruciferae (10.2%), Leguminosae (8.3%) and Boraginaceae (6.8%), followed by Caryophyllaceae and Gramineae (5.4%). These six families represent 60% of the total families recognized in the study area, while nine families each are represented by only one species. Most plants recorded are annual plants (61%), some plants are hemicryptophtes (18%) and camaephytes (15%), while the least frequent life form class was the phanerophyte shrub and perennial (0.5%). Chorological characteristics of the recorded flora show that Saharo-Arabian Region elements, IranoTuranian elements and Mediterranean elements constitute (58%) of the total flora. This research shows that even small portion of the Jordan Badia such as the Wadi Hassan plant community has high species diversity. Thus, we recommended further of the unexplored Wadi plants communities of the Jordan Badia.
Keywords: Arid zone    Badia    Wadies    Wadi hassan    Life form    Chorology    
1. Introduction

Ephemeral streams are common features of landscapes around the world, and are the predominant fluvial environments in arid zones (Shaw and Cooper, 2008). In most arid land systems, vegetation cover rarely exceeds 75% and bare soil is always a significant feature (Huxman et al., 2004). Plant ecosystems in arid and semiarid climates, however, show high complexity, especially in areas where water availability allows plants to carry out vital processes (Quevedo and Francés, 2008). Yet, because dominant plant communities and habitat types change according to soils and precipitation (Zhang et al., 1999, Obando, 2005, Stromberg et al., 2007, Skirvin et al., 2008), assessing the plant diversity of ephemeral stream plant communities has proven challenging.

Jordan consists not only of desert, but also semi-desert and steppe called the Jordanian steppe, or Badia. Badia, unlike typical deserts, have clay and are covered by gravels or pebbles (Al-Eisawi, 1996). Vegetation in the Badia is scarce to non-existent. When present, plant cover consists of fleshy plants restricted to the watersheds of ephemeral streams called wadies, where soil moisture is sufficient to support vegetation. Badia of northeast Jordan are particularly fragile. As a consequence, habitat degradation and species losses in this region have been severe, reducing biodiversity at rates that far exceed natural processes (Ministry of Agriculture, 1996).

Although 80% of the total area (90, 000 km2) of Jordan is desert, the flora of Jordan is diverse. Previous studies have identified between 2543 and 2978 plant species belonging to between 120 and 142 families and 719 to 868 genera (Al-Eisawi, 2013). Continued floristic studies, especially of wadi plant communities, would help accurately assess plant diversity of Jordan's Eastern Badia.

The goal of the present work is to study the floristic composition, life forms, and chorology of the Wadi Hassan watershed in the Azraq Basin (Eastern Badia). This study may help better understanding whether vegetation can be used in the future as a major tool for watershed management.

2. Materials and methods 2.1. The study area

Wadi Hassan is located in the eastern Badia of Jordan (31° 97′ N, 36° 89′ E), in the north western part of the Al-Azraq area. The Wadi is a part of one of the largest catchment areas in the northern Badia of Jordan (≈360 km2). The main catchment consists of three main wadies; the largest of them begin in the Syrian Jebal Al–Arab north of Jordan and is joined by the other two wadies near the Southern edge of the catchment. Wadi Hassan stretches from Jebal Al-Asfar in the east. All the wadies reach a mud flat locally known as Marab Hassan. Downstream, one wadi continues to the Azraq mud flat (Qa'a Al-Azraq) and has an elevation gradient 580 m–610 m. Soil is composed of basaltic volcanic rock, which has a texture that ranges between silty clay and course sand, and a pH between 7.5 and 8.3; soil salinity ranges from 0.5 to 7.4 mM/cm (Fig. 1).

Fig. 1 (A) Map of Jordan showing the location of Wadi Hassan and pictures taken during the study period (2010/2011). (B) Wadi Hassan catchment and sub-catchment areas (31°N, 36°E; Al-Ayyash et al., 2012).

The climate of the Northeastern Badia is arid with a mean annual rainfall increasing from 50 mm per year in the south to over 250 mm per year in the north near the Syrian border (Fig. 2). The rainy season lasts from October through April. On average, there are 23 rainy days; the average annual rainfall for the catchment is 194 mm and for Wadi Hassan is 50 mm (Fig. 2, Fig. 3).

Fig. 2 Annual Precipitation and Mean Daily Temperature for Wadi Hassan, 2000–2009 (Data collected from Meteorological Department/Amman/Jordan).

Fig. 3 Precipitation and Mean Daily Temperature at Wadi Hassan, 2011 (Data collected from Meteorological Department/Amman/Jordan).

January is the coldest month of the year, during which the average monthly temperature can fall below 0 ℃. The hottest months are July and August with an average temperature of 29 ℃. The mean annual temperature is about 20 ℃. The temperature gradually increases from January to July and starts to decrease from August to December. Summer temperatures rarely rise above 40 ℃ while winter temperatures may drop to 0 ℃ (Fig. 3).

2.2. Data collection

The present inventory includes all vascular plant taxa growing at Wadi Hassan. This inventory is based on plant taxonomy references, pictorial floras, and comparisons with herbarium specimens at the University of Jordan (El-Oqlah and Taifour, 2017, Al-Eisawi, 2013, Zohary, 1966, Zohary and Feinbbrun-Dothan, 1972, Koppel et al., 1977, Koppel et al., 1986, Al-Eisawi, 1982, Al-Eisawi, 1986, Al-Eisawi, 1998, Cope and Al-Eisawi, 1998). This list, which is largely based on personal collections from March 2010 until December 2011, integrates data obtained from studying available collection in the Badia herbaria. Voucher specimens have been deposited at the University of Jordan's Department of Biology, in the Faculty of Sciences. We used Zohary's (1973) terminology to describe chorological units.

3. Results and discussion

The floral diversity of Wadi Hassan is rich, including numerous valuable plant species. The checklist of plant species from this study area includes 206 species belonging to 138 genera and 34 families (Table 1). The most diverse families are Compositae (20.5%), Cruciferae (10.2%), Leguminosae (8.3%), Boraginaceae (6.8%), followed by Caryophyllaceae and Gramineae (5.4% the same for both families). These six families represent 60% of the total families recognized in the study area (Fig. 4). Of 34 families identified at Wadi Hassan, 26.5% (9 families) of the total number of families, are represented by one species per family. This common feature of desert flora indicates that only a few of the large number of species that belong to these plant families have adapted to the harsh desert environment.

Table 1 Checklist of Wadi Hassan 206 species belong to 138 genera and 34 families, ordered alphabetically.
Family Species Life form Summer Shedding Chorotype
Aizonaceae 1. Aizoon hispanicum L. Annual Ephemeral SA
2. Mesembryanthemum nodiflorum L. Annual Ephemeral ES, M, SA
Amaranthaceae 3. Amaranthus albus L. Annual Ephemeral A
4. A. blitoides S. Wats. Annual Ephemeral A
5. Halogeton alopeauroides(Del.) Moq. Chamaephyte Perenating SA
Boraginaceae 6. Anchusa aegyptiaca (L.) DC. Annual Ephemeral SA
7. A. milleri Willd. Annual Ephemeral IT, SA
8. A. ovata Lehm Annual Ephemeral IT
9. Arnebia hispidissima(Lehm.) DC. Annual Ephemeral SA, SU
10. A. linerarifolia DC. Annual Ephemeral IT, SA
11. A. tinctoriaens Forssk. Annual Ephemeral SA
12. Gastrocotyle hispida (Forssk.) Bunge Geophyte Ephemeral IT, SA
13. Heliotropium bacciferum Forssk. Chamaephyte Perenating SA, SU
14. H. europaeum L. Annual Ephemeral M, I, T
15. H. hirsutissimum Grauer Annual Ephemeral M
16. L. muricata Annual Ephemeral SA
17. L. spinocarpos (Forssk.) Aschers. Annual Ephemeral IT, SA
18. Nonea ventricosa (Sm.) Griseb. Annual Ephemeral M, IT
19. Paracaryum rugulosum(DC) Boiss. Hemicryptophyte Ephemeral IT, SA
Capparaceae 20. Capparis ovata Desf. Chamaephyte Perenating M, IT, SA
Caryophyllaceae 21. Dianthus judaicus Boiss. Hemicryptophyte Perenating IT
22. Gypsophila arabica Barkoudah. Chamaephyte Perenating IT
23. Herniaria hirsuta L. Annual Ephemeral ES, M, IT
24. Minuartia picta Bornm Annual Ephemeral IT
25. Paronychia argentea Lam. Hemicryptophyte Perenating M
26. Pteranthus dichotomus Forssk. Annual Ephemeral SA
27. Silene colorata Poir. Annual Ephemeral M
28. S. conoidea L. Annual Ephemeral M, IT
29. S. arabica Bioss Annual Ephemeral SA
30. Spergula fallax (Lowe) karuse Annual Ephemeral SA
31. Spergularia diandra(Guss.) Heldr. Et Sart. Annual Ephemeral M, IT, SA
32. Vaccaria pyramidata Medik. Annual Ephemeral M
Chenopodiaceae 33. Anabasis setifera Moq. Chamaephyte Perenating SA
34. A. syriaca Iljin. Chamaephyte Perenating IT
35. Atriplex leucoclada Boiss. Chamaephyte Perenating IT, SA
36. Bassia eriophora(Schrad.) Ascherus Annual Ephemeral SA, SU
37. B. muricata (L.) Aschers. Annual Ephemeral IT, SA
38. Halothamnus acutifolius(Moq.) Botsch. Chamaephyte Perenating IT
39. Hammada eigii Iljin Chamaephyte Perenating IT
40. Salsola volkensii Schweinf. et Aschers. Annual Ephemeral SA
41. Seidlitzia florida (M. Bieb.) Boiss. Chamaephyte Ephemeral SA
42. S. rosmarinus Beg. ex. Boiss Chamaephyte Ephemeral SA
Cistaceae 43. Helianthemum sessiliflorum (Desf.) Pers. Chamaephyte Perenating SA
Compositae 44. Aaronsohnia factorovskyi Warb. & Eig. Annual Ephemeral SA
45. Achillea fragrantissima(Forssk.) Sch. Bip Hemicryptophyte Perenating IT, SA
46. A. membranacea (Labill.) DC. Hemicryptophyte Perenating
47. Anthemis bornmulleri Stoj. & Acht. Annual Ephemeral M
48. A. haussknechtii Boiss. & Reut. Annual Ephemeral IT
49. Artemisia herba-alba Asso Chamaephyte Perenating IT
50. Asteriscus pygmareus(DC.) Coss. & Dur. Chamaephyte Perenating SA
51. Atractylis cancellata L. Annual Ephemeral M
52. A. prolifera Boiss Annual Ephemeral SA
53. Calendula arvensis L. Annual Ephemeral M, IT
54. C. tripterocarpa Rupr. Annual Ephemeral SA
55. Carduus getulus Pomel Annual Ephemeral SA
56. Carthamus tenuis (Boiss & Bl.) Bornm Annual Ephemeral M
57. Centaurea aegyptiaca L. Chamaephyte Perenating SA
58. C. ammocyanus Boiss. Annual Ephemeral SA
59. C. lanulata Eig Hemicryptophyte Ephemeral SA
60. Crepis aspera L. Annual Ephemeral M
61. C. sancta (L.) Bornm. Annual Ephemeral M, SA
62. Echinops glaberrimus DC. Hemicryptophyte Perenating SA
63. Filago contracta (Boiss.) Chrtek & Holub Annual Ephemeral IT
64. F. desetorum Pomel Annual Ephemeral IT, SA
65. Gymnarrhena micrantha Desf. Annual Ephemeral SA
66. Ifloga spicata (Forssk.) Sch. Bip. Annual Ephemeral SA
67. Lactuca orientalis(Boiss.) Boiss. Hemicryptophyte Perenating IT
68. L. serriola L. Annual Ephemeral ES, M, IT
69. Lasiopogon muscoides(Desf.) DC. Annual Ephemeral SA
70. Launaea mucronata(Forssk.) Muschler Annual Ephemeral SA
71. L. nudicaulis (L.) Hook. fil. Hemicryptophyte Perenating SA
72. Leontodon laciniatus(Bertol.) Widder Annual Ephemeral IT, SA
73. Matricaria aurea (Loefl.) Sch. Bip. Annual Ephemeral M, IT
74. Notobasis syriaca (L.) Cass. Annual Ephemeral M
75. Onopordum alexandrinum Boiss. Hemicryptophyte Ephemeral IT, SA
76. O. transjoranicum Eig. Hemicryptophyte Ephemeral SA
77. Phagnalon rupestre (L.) DC. Chamaephyte Perenating M, IT
78. Picnomon acarna (L.) Cass. Annual Ephemeral M, IT
79. Picris asplenioides Annual Ephemeral SA
80. P. cyanocarpa Boiss Annual Ephemeral SA
81. Reichardia tingitana (L.) Roth Annual Ephemeral M, IT
82. Scorzonera papposa DC. Hemicryptophyte Ephemeral IT
83. S. pusilla Pall. Hemicryptophyt Ephemeral IT
84. S. schweinfurthii Boiss Hemicryptophyt Ephemeral SA
85. Sonchus oleraceus L. emend. Gouan Annual Ephemeral ES, M, IT
86. Zoegea purpurea Fresen Annual Ephemeral IT, SA
Convolvulaceae 87. Convolvulus lanatus Vahl Chamaephyte Perenating SA
Cruciferae 88. Alyssum marginatum Steud. ex Boiss. Annual Ephemeral IT
89. A. meniocoides Boiss. Annual Ephemeral IT
90. Biscutella didyma L. Annual Ephemeral M, IT
91. Diplotaxis erucoides (L.) DC. Annual Ephemeral M
92. D. harra (Forssk.) Bioss. Chamaephyte, Hemicryptophyte, Annual Ephemeral SA
93. Eruca sativa Mill. Annual Ephemeral M, IT
94. Erucaria boveana Coss. Annual Ephemeral SA
95. E. pinnata Annual Ephemeral SA
96. Lepidium aucheri Boiss. Annual Ephemeral IT
97. Lobularia arabica(Boiss.) Muschl. Annual Ephemeral SA
98. Malcolmia africana (L.) R. Br. Annual Ephemeral IT, SA
99. M. conringioides Bossi Annual Ephemeral IT, SA
100. Matthiola aspera Boiss. Annual Ephemeral SA
101. M. paviflora (Schousb.) R. Br. Annual Ephemeral SA
102. Notoceras bicorne (Sol.) Caruel Annual Ephemeral SA
103. Schimpera arabica Hochst. Et Steud. ex Boiss Annual Ephemeral SA
104. Sinapis alba L. Annual Ephemeral ES, M, IT
105. S. arvensis L. Annual Ephemeral M
106. Sisymbrium runcinatum Lag. Annual Ephemeral IT
107. S. septulatum DC. prol. bilobum (C. Koch) O. E. Schulz Annual Ephemeral IT
108. Zilla spinosa (L.) Prantl Chamaephyte Perenating SA
Cucurbitaceae 109. Citrullus colocynthis (L.) Schrad. Hemicrytophyte Perenating SA
Dipsacaceae 110. Scabiosa porphyroneura Blakelock Annual Ephemeral IT, SA
Euphorbiaceae 111. Andrachne telephioide L. Hemicrytophyte Perenating M, IT
112. Chrozophora oblongifolia (Del.) Ad. Juss. ex Spreng Chamaephyte Perenating SU
113. C. obliqua (Vahl) Ad. Juss. Annual Ephemeral M, IT
114. C. plicata (Vahl) Ad. Juss. ex Spreng Annual Ephemeral SU
115. Euphorbia chamaepeplus Boiss. et Hohen Annual Ephemeral IT, SA
116. E. terracina L. Hemicrytophyte Perenating M
Geraniaceae 117. Erodium bryoniifolium Boiss. Annual Ephemeral SA, SU
118. E. deserti (Eig) Eig Annual Ephemeral SA
119. E. laciniatum (Cav.) Willd. Annual Ephemeral M
Gramineae 120. Bromu danthoniae Trin. Annual Ephemeral IT
121. B. scoparius L. Annual Ephemeral M, IT
122. Crithopsis delileana(Schult. & Schult. fil.) Roshev Annual Ephemeral M, IT
123. Cynodon dactylon (L.) Pers. Chamaephyte, Geophyte Perenating TR
124. Hordeum glaucum Steud. Annual Ephemeral M, IT
125. Poa bulbosa L. Hemicryptophyte Ephemeral ES, M, IT
126. Polypogon viridis(Gouan) Breistr. Hemicryptophte Perenating M, IT
127. Schismus arabicus Nees. Annual Ephemeral IT, SA
128. Stipa capensis Thunb. Annual Ephemeral IT, SA
129. S. parviflora Desf. Hemicryptophte Perenating IT
Iridaceae 130. Iris sisyrinchium L. Geophyte Ephemeral M, IT
Lamiaceae 131. Ballota undulata (Sieb. ex Fresen) Benth. Chamaephyte Perenating M
132. Eremostachys transjordanica Eig. Hemicryptophte Ephemeral IT
133. Phlomis brachyodon Boiss. Chamaephyte Perenating M
134. Salvia lanigera Poir. Chamaephyte Perenating M, SA
135. S. spinosa L. Hemicryptophte Ephemeral IT
136. Teucrium montbretii Benth. Hemicryptophte Perenating M, IT
137. Thymus bovei Benth. Chamaephyte Perenating SA
Leguminosae 138. Astragalus alexandrines Boiss Hemicryptophyte Ephemeral SA
139. A. annularis Forssk Annual Ephemeral SA
140. A. bombycinus Bioss. Annual Ephemeral SA
141. A. corrugatus Bertol. Annual Ephemeral IT, SA
142. A. palaestinus Eig. Hemicryptophyte Ephemeral M, IT
143. A. sieberi DC. Chamaephyte Perenating SA
144. A. sparsus Del. Hemicryptophyte Ephemeral SA
145. A. spinosus (Forssk.) Muschl. Chamaephyte Perenating IT
146. A. trachoniticus Post Annual Ephemeral
147. A. tribuloides Del. Annual Ephemeral IT, SA
148. Hippocrepis unisiliquosa L. Annual Ephemeral M
149. Medicago laciniata (L.) Mill. Annual Ephemeral SA
150. Onobrychis caput-galli(L.) Lam. Annual Ephemeral M
151. O. wettsteinii Nab. Hemicryptophyte Ephemeral IT
152. Retama raetam(Forssk.) Webb Phanerophyte shrub Perenating SA
153. Trigonella caelesyriaca Boiss. Annual Ephemeral M
154. T. monspeliaca L. Annual Ephemeral M
155. T. stellate Forssk. Annual Ephemeral SA
Liliaceae 156. Allium ampeloprasum L. Geophyte Ephemeral M, IT
157. A. artemisietorum Eig & Feinbr. Geophyte Ephemeral IT
158. A. desertorum Forssk. Geophyte Ephemeral SA
159. A. qasyunense Mout. Geophyte Ephemeral IT
160. A. stamineum Boiss Geophyte Ephemeral M, IT
161. Bellevalia zoharyi Feinbr Geophyte Ephemeral IT
162. Urginea maritime (L.) Baker Geophyte Ephemeral M
Malvaceae 163. Hibiscus trionum L. Annual Ephemeral TR
164. Malva parviflora L. Annual Ephemeral M, IT
165. M. sylvestris L. Hemicryptophyte Ephemeral M, ES
Papaveraceae 166. Glaucium arabicum Fresen. Hemicryptophyte Perenating IT
167. Hypecoum pendulum L. Annual Ephemeral M, IT
168. Papaver syriacum Boiss. et. Bl. Annual Ephemeral M
169. P. subpiriforme Fedde Annual Ephemeral M
170. Roemeria hybrida (L.) DG. Annual Ephemeral M, IT
Plantaginaceae 171. Plantago amplexicaulis Cav. Annual Ephemeral SA
172. P. bellardii All. Annual Ephemeral M, IT
173. P. cretica L. Annual Ephemeral M
174. P. notate Lag. Annual Ephemeral IT, SA
175. P. ovata Forssk. Annual Ephemeral IT, SA
Polygonaceae 176. Emex spinosa (L.) Campd. Annual Ephemeral M
177. Rumex cyprius Murb. Annual Ephemeral IT, SA
Primulaceae 178. Anagallis arvensis L. Annual Ephemeral ES, M, IT
179. Androsace maxima L. Annual Ephemeral M, IT
180. Samolus valerandi L. Hemicryptophyte Perenating TR
Rafflesiaceae 181. Cytinus hypocistis (L.) L. Hemicryptophyte, parasite Ephemeral M
Ranunculaceae 182. Adonis dentate Del. Annual Ephemeral IT, SA
Resedaceae 183. Caylusea hexagyna(Forssk.) Green Annual Ephemeral SU
184. Oligomeris subulata(Del.) Boiss. Annual Ephemeral SU
185. Reseda alba L. Annual Ephemeral M, IT
186. R. muricata C. Presl Chamaephyte Perenating SA
Rubiaceae 187. Callipeltis aperta Boiss & Buhse Annual Ephemeral IT, SA
188. Galium chaetopodum Rech. fil. Annual Ephemeral M
Rutaceae 189. Haplophyllum blanchei Boiss. Chamaephyte Perenating M, IT
190. H. tuberculatum(Forssk.) Ad. Juss. Chamaephyte Perenating SA
Scrophulariaceae 191. Kickxia aegyptiaca (L.) Nábělek Chamaephyte Perenating M, SA
192. Linaria albifrons (Sm.) Spreng. Annual Ephemeral IT
193. Verbascum transjordanicum Murb Hemicryptophyte Perenating IT
Solanaceae 194. Solanum luteum Mill Hemicryptophyte Ephemeral ES, M, IT
Umbelliferae 195. Anisosciadium isosciadium Bornm. Annual Ephemeral SA
196. Bupleurum lancifolium Hornem. Annual Ephemeral M, IT
197. Chaetosciadium trichospermum (L.) Boiss. Annual Ephemeral M
198. Ducrosia flabellifolia Boiss. IT, ES
199. Pimpinella eriocarpa Banks et Sol. Annual Ephemeral IT
200. Psammogeton setifolium(Boiss.) Boiss. Annual Ephemeral
Urticaceae 201. Parietaria lusitanica L. Annual Ephemeral M
202. Urtica pilulifera L. Annual Ephemeral ES, M, IT
Zygophyllaceae 203. Fagonia bruguieri DC. Chamaephyte Perenating SA
204. F. glutinosa Del. Chamaephyte Perenating SA
205. Peganum harmala L. Hemicryptophyte Perenating IT, SA
206. Tribulus macropterus Boiss. Hemicryptophyte Perenating SU
The chorotypes are: A, American; IT, Irano-Turanian; ES, Euro-Siberian; M, Mediterranean; SA, Saharo-Arabian; SU, Sudania; TR, Tropical.

Fig. 4 The plant family diversity in Wadi Hassan/Eastern Desert. The most diverse families are Compositae (20.5%), Cruciferae (10.2%), Leguminosae (8.3%), Boraginaceae (6.8%), followed by Caryophyllaceae and Gramineae (5.4% the same for both families). These six families represent 56.6% of the total families recognized in the study area.

Our survey of Wadi Hassan identified numerous plants of special interest. Notably, many of the plant species recorded from Wadi Hassan are medicinal herbs (e.g., Achillea fragrantisima, Artemisia herba-alba, Paronychia argentea, Teucrium montbretii, Thymus bovei, Glaucium arabicum, Citrullus colocynthis, Anagallis arvensis, Plantago ovata) used in folk medicine. In addition, several toxic (poisonous) plant species were found in the study area, including C. colocynthis, Urginea maritime, and the African rue Peganum harmal. Some of the recorded species are endemic to Jordan such as Eremostachys transjordanica, and some of these species (e.g., Ducrosia flabellifolia) are rare.

In Jordan Badia, most of the area appears to the casual observer to be without vegetation cover all. According to the flora survey conducted by the Azraq Project (Al-Eisawi, 1995), terrestrial plant communities comprise 133 species of vascular plants, belonging to 100 genera and 33 families. Seven species were recorded as new to the flora of Jordan and unique to the Azraq Wetland Reserve. However, the previous checklist for the flora of the Eastern Badia stands only at 322 plant species in 46 families (Cope and Al-Eisawi, 1998, Dutton et al., 1998).

Due to the scarcity of water and nutrients, most of the plant species identified by our checklist are restricted to small time periods and at select sites. These species may have been successful at maintaining high diversity because of strong root systems, which facilitate absorption of moisture as well as nutrients from different soil types (Ahmad et al., 2009, Hussain, 2002).

The Wadi Hassan flora exhibit a great diversity of life forms typical of desert flora. Most plants recorded are annual plants (61%), some plants are hemicryptophtes (18%) and camaephytes (15%), few are geophytes (5%) and phanerophyte shrub composed only 0.5% (Fig. 5). Furthermore, Retama raetam was one of the most common species recorded during the two-year collection period (2010/2011). R. raetam is the only phanerophyte shrub recorded in Wadi Hassan and the maximum vegetation height for the study area (245 cm) can be attributed to the presence of this plant.

Fig. 5 Life form of plant species recorded in Wadi Hassan checklist 2010/2011.

Arid vegetation community structure, function, patterns of species colonization, and succession are highly determined by climatic factors. On an annual scale, precipitation pattern and intensity affect floristic composition and biomass; even rainfall events less than 5 mm can play a vital role in affecting species composition (Westbrookea et al., 2005, Fariz and Hatough-Bouran, 1998). Recruitment of some long-lived species is probably confined to very rare occasions when soil water reservoirs are substantial enough to allow the growing taproot of seedlings to reach soil depths with reliable ground water (Westbrookea et al., 2005). Furthermore, the mortality of perennials is affected by periods of limited water availability (Milton and Dean, 2000). Finally, the abundance of annuals is largely, determined by the amount of rainfall (Ward et al., 2000). Our finding that 60% of plants in Wadi Hassan are annuals and 73.2% are ephemeral plants agrees with these previous studies. Moreover, the highest vegetation cover in Wadi Hassan occurs in the same area where soil moisture was the highest, except in the area where soil crust formed. The low percent of phanerophytes recorded in this study in consistent with the floristic composition of the Khulais region, West Saudi Arabia (Alsherif et al., 2013) and are in agreement with previous observation that south and south-western Arabian Peninsula are very poor in tree (White and Leonard, 1991).

Short-term dynamics in arid/semi-arid systems have been relatively well studied. For example, annuals are thought to act as opportunists; they have short life spans and high fecundity, traits which enable these plants to rapidly colonize open spaces generated by disturbances (Gupta and Narayan, 2006). Annuals are also well-known to respond strongly to interannual variation in rainfall (Bowers, 1987, Hobbs and Mooney, 1995, Guo and Brown, 1996).

Figure 6 shows the chorological characteristics of Wadi Hassan flora. Saharo-Arabian region elements recorded the highest number (29%) followed by Irano-Turanian elements (15%) and Mediterranean elements (14%). In addition to plant species that belong to the Mediterranean and the Irano-Turanian elements presented in the target region, it has a large number of plant species which dominate in other uniregional region, such as Saharo-Arabian. American and Tropical elements showed the least species number (2 and 3 species, respectively).

Fig. 6 Proportional percentage of chorological types of the recorded species. A, American; IT, Irano-Turanian; ES, Euro-Siberian; M, Mediterranean; SA, Saharo-Arabian; SU, Sudania; TR, Tropical.

The high species number of Saharo-Arabian elements can likely be explained by the adaptation of these plant species to the aridity and high temperatures of harsh environments similar to the Jordan Badia. Vegetation cover is mainly concentrated in locations where water accumulates. These results are in agreement with studies in Saudi Arabia (Al-Turki and Al-Qlayan, 2003, El-Ghanem et al., 2010, Alatar et al., 2011, Daur, 2012, Alsherif et al., 2013).

4. Conclusion

The present study is the first floristic study of Wadi Hassan and shows the importance of plant diversity in this region. The numbers of species in this region are high, largely because of soil characteristics and water availability. Although we have identified high plant diversity in one small region, this study only reflects a glimpse of the plant diversity of the larger area. Thus, we believe many plant species remain unrecorded and need long-term comprehensive study.

None declared.

This work was supported by the Biology Department, University of Jordan, Amman. The authors, therefore, acknowledge with thanks University of Jordan support for Scientific Research. We thank our colleagues from Department of Land, Water and Environment, University of Jordan and in the Jordan Badia Research and Development Center, especially who provided insight and expertise that greatly assisted the research.

Supplementary data to this article can be found online at

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