الفهرس 
Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
The thesis deals with the plant life in Wadi Araba area which belongs to the
Galala Desert ”Dg” and the Red Sea coast ”R” phytogeographical territories (El-Hadidi, 1993d). The study area includes the main bed of Wadi Araba and some of its important tributaries in ( Wadi Abu-Khodirate, Wadi Askhar&Wadi Irkase) North and South Galalas.
A total of 127 species belonging to 97 genera and 36 families of seed plants were recorded in the study area. Gymnosperms are represented by one species viz. Ephedra alata. Among Angiosperms, the Dicotyledons are represented by 113 species belonging to 84 genera and 31 families. Fagonia is the largest genus represented by six species, followed by Launaea represented by five species, while Astragalus is represented by four species. Genera represented by three species each are: Atriplex, Cleome, Erodium, Zygophylhim and Plantago. Genera represented by two species each are: Tribulus, Euphorbia, Helianthemum, Deverra, Hcliotropium, Pulicaria and Artemisia. Monocotyledons are represented by 13 species belonging to 13 genera and four families.
The larger families in the study area are: Compositae (20 species), Leguminosae (12 species), Gramineae (11 species), Chenopodiaceae (9 species), Zygophyllaceae (9 species), Cruciferae (7 species) and Boraginaceae (7 species).
Life-forms of the recorded species comprise: 10 phanerophytes, 33 chamaephytes, 32 hemicryptophytes, five hemicryptophytes and/or therophytes, seven geophytes, 39 therophytes and one parasite species.
Only 30 species were recorded from the main bed of Wadi Araba, 34 species were recored from the Galala sectors of the study area (13 species in the North Galala, 11 species in the South Galala and 10 species in both sectors). Another 34 species were recorded from the three sectos of the study area.
A total number of 76 species were in the South Galala sector which is higher than that recorded in the North Galala sector (65 species). So the flora of the main bed of Wadi Araba is more influnced by South Galala than to North Galala.
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Thirty two species ( or 25.2%) of the recorded species are monoregional Saharo-Sindian taxa. Biregional Saharo-Sindian taxa extending to Sudano-Zambezian, Irano-Turanian or Mediterranean territories are represented by 24 species, 20 species and 4 species respectively; constituting together 37,8% of the recorded species. Tri-or pluriregional Saharo-Sindian taxa extending to adjacent regions (Irano-Turanian, Sudano-Zambezian and Mediterranean ) are represented by 31 species (or 24.1 %) of the recorded species.
Accordingly Saharo-Sindian elements are apparently well represented in the study area with I! 1 species (or 87.4%) of the recorded species, 66 species grow in the South Galala and 60 species grow in the North Galala.
Six species (or 4.8%) of the recorded species belonging to Guineo-Congo, Madagascan, Karoo, Euro-Sibarian and Cape elements are few (or 4.8%) of the recorded species). Cosmopolitan and Pantropical taxa are few 6 species or 4.8% of the recorded species) and comprise mesic plants which were recorded in the moist places (around birs) of the study area.
Launaea tenuiloba is the only monoregional Mediterranean taxon recorded from the study area while Fibigia clypeata is a Mediterranean taxon extending to west Irano-Turanian region. Podonosma galalensis and Echinops gatalensis are endemic species, the former is confined to the North Galala mountain while the latter grows in both of the N&S Galala Deserts.
Fourteen plant communities are distributed in the main bed of Wadi Araba and its tributaries (Wadi Abu-Khodirate, Wadi Askhar and Wadi Irkase). The physical characters of the soil especially soil depth and soil texture which greaty control the water content of the soil are the main factors for the distribution of these communities in the study area. Six communities are recorded in each of Wadi Abu-Khodirate and Wadi Irkase, eight communities were recorded in the main stream of Wadi Araba and four plant communities were recorded in Wadi Askhar.
Four communities, viz. Hammada elegans, Pulicaria crispa, Retama raetam&Zilla spinosa) are the most widely distributed in the study area. Hammada elegans community grows in different parts of Wadi Irkase, Wadi Askhar and in the main stream of Wadi Araba where the soil is of deep sandstone fine elements. This
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community tolerates high salinity and was recorded near the wells of Bir El-Bouirate and Bir El-Zafarana, also near the coastal plain of the Suez Gulf. Pulicaria crispa community grows in Wadi Abu-Khodirate, Wadi Irkase and in the main stream of Wadi Araba . It grows on comparatively shallow soil of chalky gravel elements or on deep soil of fine sandstone elements. Retama raetam community grows in the upstream parts of Wadi Irkase, in the main stream of Wadi Araba and in the downstream part of Wadi Askhar where the soil is of deep sandstone elements. The dominant plant of this community (Retama raetam) gives the vegetation of the South Galala and related terraces of Wadi Araba its physiognomy . Zilla spinosa community grows in the downstream parts of Wadi Abu-Khodirate where the soil is of gravel limestone and in the main stream of Wadi Araba where the soil consists of deep fine sandstone elements.
Two communities (Fagonia arabica&Panicum turgidum) were recorded
from the main stream of Wadi Araba and one of its tributaries. Fagonia arabica community grows in the downstream of Wadi Irkase and in the main stream of Wadi Araba where the soil is composed of coarse sand elements. Panicum turgidum community grows in the runnels of the main stream of Wadi Araba in Bir Araiyida area, also in the runnels of Wadi Askhar. This community grows on both sandstone and limestone substratum.
Acacia tortilis community dominated the upstream parts of Wadi Abu-Khodirate and Wadi Askhar where the soil is chalky of deep gravels or boulders . The dominant plant of this community (Acacia tortilis) gives the vegetation of the North Galala its physiognomy, this community was described as desert open foresAt (cf. Kassas&Girgis(1970).
Centaurea scoparia, Launaea spinosa and Zilla spinosa/Launaea spinosa communities were restricted to Wadi Abu-Khodirate. Two communities viz. Zilla spinosa/Euphorbia retusa and Panicum turgidum/Pulicaria crispa were recorded from the main stream part of Wadi Araba. Another two communities viz. Pulicaria crispa/Hammada elegans and Pennisetum divisum were recorded from the down stream part and upstream parts of Wadi Irkase respectively.
Wadi Irkase has the largest number of the recorded annual species (29); the occurrence of these annual species in the main stream of Wadi Araba and in the
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downstream of Wadi Irkase can be attributed to the run-off water of torrents which is strong enough to reach these parts.
Rare annual species were recorded only from the upstream rocky parts of Wadi Abu-Khodirate viz. Paracarym intermedium, Podonosma galalensis, Gypsophilla cappiiaris, Lasiopogon muscoides, Senecio glaucus, Reichardia tingitana and the endemic species Podonosma galalensis. Other rare annual herbs were recorded only from Wadi Irkase, viz. Savignya parviflora, Cutandia memphitica, Plantago ovata, Diplotaxis harra, Sonchus oleraceus,and the mediterrnean species Launaea tenuiloba&Fibigia clypeata and Sonchus oleraceus.
Wadi Irkase has the largest number of the recorded annual species (29); the occurrence of these annual species in the main stream of Wadi Araba and in the downstream of Wadi Irkase can be attributed to the run-off water of torrents which is strong enough to reach these parts.
Wadi Abu-Khodirate has the greatest value of species diversity as it has a species richness of 30 species , (17.1±3.4) species/stand. It has a simpson index of (0.94±0.27) and a vegetation denesity of (0.5+0.23) ind./m2 .Wadi Araba has a comparatively lower value of species diversity with a species richness of 27 species (9.4±2.8) species/stand. It has a simpson index of (1,9±0.9), and a vegetation density of (0.37+0.21) ind./m2.Wadi Irkase was intermediate as it has a species richness of 30 species (13.1+2.3) species/stand. It has a simpson index of (1.6±0.7) and a vegetation density of (0.39+0.14) ind./m2.
Species diversity results from a synthesis of properties related to the origin and history of ecosystems, and their current organization and function. Diversity can be used to describe the results of the action of a multiplicity of factors (El-Demerdash, 1996).The high species diversity of Wadi Abu-Khodirate over Wadi Irkase and Wadi Araba can be attributed to the preference of the recorded perennial species to the limestone substratum rather than the sandstone substratum. Also, many of these species find their requirements in the limestone habitat with gravel element and not in the sandy habitat with fine soil particles. Then, Wadi Abu-Khodirate is characterized variety of habitats viz. rocky bed, crieves with soft soil pockets, discontinous shallow soil, shallow soil with coarse elements and deep soil with coarse elements.