Floristic Compositions and its Affinities to Phytogeographical Regions in Wadi Khulab of Jazan, Saudi Arabia

Wadi Khluab considersone of the most important wadis in Jazan, south-western Saudi Arabia. Thus the current work provides an analysis of thefloristic composition, life form and chorology of plant life of the wadi, a total of 119 species related to 93 genera represented 44vascular plants families were documented. Six families (Aizoaceae, Euphorbiaceae, Papilionaceae, Poaceae, Amaranthaceae and Asclepediaceae) provided nearly half of the total number of species reported. Therophytes and chamaephytes are the most frequent life forms which may indicating a typical desert spectrum vegetation. The floristic composition of the different geomorphologic landscape units offered differences in species richness in the different sectors of the wadi, and the phytochoria. Monoregional andbiregional areascontained 45 species (41 %), while biregional species were 39 species (36 %) respectively, while only two species (2 %) were recorded in the pleuriregion. It is thus concluded that the region should be consideredahotspotintheKingdomintermsof floraldiversity.

. There is no earlier reports on the vegetation which reflecting of the exciting environmental conditions of the Wadi Khulabso this study needed to survey and identification of the wild plants growing in the wadi and to study the vegetationtypes in terms of floristiccomposition,life-form and chorotype.
It l i e sbetween16°46'0"Nlatitudeand 43°16'0"Elongitude(Figure1).Thestudyarea,approximately 40-50 km 2 long lies 70 meters above sea level. It is considered to be favorable for plant growth due to stagnant water after rainfall. According to Walter et al. (1975),thestudyarealieswithinthesubtropicaldryzone,andhasveryhotsummersand mildwinters.Theaverageannualtemperature is 31.3°C; January and February are the coldest months with the lowest average temperature (26 0 C), while the hottest months is August with the highest average temperature (40°C). The maximum precipitation (12.0 mm) falls during August, while the minimum of about 5.0 mm falls during January( Figure 2, Table 1).

Floristic Composition
A total of 119 taxa belonging to 93 genera and 44 families of phanerogams, were recorded in the 28 different surveyed sectors of Wadi Khluab. Their generic representations are quite variable. In terms of species richness, the Poaceae (Gramineae) was the most abundant family comprising 20% of the total taxa ( Figure 3 and Table 2), with 24 species related to 19 genera (Table 2). These floristic findings were in accordance with those of Parker (1991) andSoulé et al. (2016.The abundance of the Poaceae might be-due to water availability, including annual precipitation and soil properties and might therefore be indicative that the Poaceae is exceedingly well-adapted to this environment.     Table 4 shows the life form spectra of the recorded species, the highest life form recorded was for the therophytes constituted by 50 species representing 42 % of the total species followed by the chaemophytes with 40 species representing 34%. Likewise, 18 species of the phanerophytes estimated represented 15%. Furthermore, six species estimated as cryptophytes (Asphodelus tenuifolius, Cyperus alopecuroides, Cyperus laevigatus, Cyperus alternifolius, Panicum turgidum and Tetrapogon tenellus) compromised 5 %. Also, four taxa of Pulicaria undulate, Cucumis prophetarum, Cucumis melo and Pennisetum setaceum seen ashemicryptophyte. Also, hydrophytes in this area represented by Typha domengensis. The five cultivated plants were represented by 5 % (Figure4). Therophytes have the highest contribution followed by chameophytes indicating the adjustment of the flora to water balance. These results are in accordance with several studies in different regions of Saudi Arabia, such as: Mosallam (2007) in Taif, Al-Turki & Al-Olayan ( 2003) in Hail region and Alatar et al.( 2012) in Wadi Al-Jufair.The predominance of phanerophytes expresses that the flora is tertiary dominated with woody plants (shrub and trees). It also displayed the level of woody flora management by the farmers using of woody species as green fertilizers and assisting natural regeneration. These results coincide with the findings of Al-Turki and Al-Olayan (2003) and Soulé et al. (2016). Danin and Orchan (1990); Abd El-Ghani (1997) and Fahmy and Hassan (2005) also reported the domination of therophytes and chaemophytes as vegetation spectra in desert and semi-desert vegetation in other parts of the Middle East. Moreover, the dominance of therophytes, chaemophytes and phanerophytes over other life forms are seen to be a response to the hot dry climate, topographic variation and human and animal interference (Abd El-Ghani and Abd El- Khalik, 2006;Al-Shammari et al., 2013). Three medicinal plants used by some local people, including Acacia tortilis, Malva parviflora and Solanum glabratum. Also, many poisonous plants such as Anagallis arvensis, Calotropis procera, Datura innoxia, Datura stramonium, Leptadenia pyrotechnica, Solanium nigrum, Tribulus terrestris and Zygophyllum simplexwere recorded.

Chorology
From the phytogeographical point of view, the recorded species in the different sectors of the studied valley may be classified as monoregional, biregional or pluriregional (Table 5). Monoregonal area has in total 45 species representing 41%, in which 20, 18 and 7 species are within the Saharo-Arabian, Sudano-Zambezian and tropical regions, respectively. The highest percentage in this area was recorded in Saharo-Arabian (18%). Biregional area included 39 species with 36% in which 29 species were shared by Saharo-Arabian and Sudano-Zambezian regions (27 %), six species were shared by Saharo-Arabian and tropical regions, and two speciesof Achyranthes aspera and Malva parviflora were recorded in the Mediterranean and Irano-Turanian regions and the two species of Anisotes triculcus and Boerhavia diffusa were estimated in the Sudano-Zambezian and tropical regions. Pleuriregional (Mediterranean,Irano-Turanian and Saharo-Arabian) area has only 2 species (Tetrapogon villosus and Setaria viridis ) representing 2 %. Also, eight species (8%) were reported within the panatropical area and six species (6 %) were recorded in paleotropical area. Cosmopolitan plants comprised 4% of the population are four species, Euphorbia hirta, Portulaca oleracea, Anagallis arvensis and Tribulus terrestris ( Figure 5). These results agree with chorological characteristic in other parts of Saudi Arabia (ALSherif, et al., 2013 on Khulais region, Abdel Khalik, et al.,2013onWadi Al-Noman andOsman et al., 2014) on Wadi Arar. The results indicate that Saharo-Arabian elements predominate the studied area (66 species, 55.5%)because this area mainly deserted and located within the belt of Saharo-Sindianalso it is a part of that belt between Saharo and Sindian.Genera ofSaharo-Arabian are covered most of the deserted area of Sindian from the red sea coast to the Gulf coast through the empty quarter desert.

CONCLUSION
Wadi Khulablocated in thesouth-westernof Saudi Arabia is floristically diverse in biodiversity. The present survey recorded 119 taxa and represented over one quarter of the checklist recorded before in Jazan area by Masrahi (2012) who identified and described bout 524 species which belong to these floristic structures. The total number of identified genera was 93 indicating a high generic index of 78 % (93/119). This high diversity in the wadi was due to the abundance of rainfall sources and soil fertility which considered as a biotic factors. The floristic composition of the wadi is rich in species, genera and botanical families due to rainfall water balance. Poaceae is the best represented botanical family followed by five families (Aizoaceae, Euphorbiaceae, Papilionaceae, Amaranthaceae and Asclepediaceae) constituted the main bulk of the wild plants in the study area. Besides that, the life forms are diverse but the therophyte and chameophytes are the dominant. The growth types in this study were perennial types were 64 species while the annual types were 55 species. Their predominance makes the phytoclimate of the wadi thero-chameophytic type. In addition, the areas of Saharo-Arabian and Saharo-Arabian and Sudano-Zambezian are the most dominant chorotypes represented more than third of total species. There are some plant species were left unrecorded hence need long-term comprehensive study to document.