1 Introduction

Egypt has a long history in vegetation research; one of the oldest researches made is by Fresenius (1834) while other studies are dating back to the 1930s (e.g. Montasir 1937; Migahid 1937; Hassib 1938; Kassas 1951; Tadros 1953). Although several regional studies on plant communities have been carried out, there has never been a compiled and complete classification overview documented with vegetation tables. On the other hand, especially in Europe, a new phase in vegetation research has been started during the last decades, resulting in building up of national databanks, publication of national overviews based on quantitative analysis, and development of new softwares for data input and techniques for data analysis (Mucina et al. 1993; Mucina 1997; Rodwell et al. 2002; Schaminée et al. 2009).

In 2008, a first international workshop was organized by Tanta University for input and management of the vegetation data. This workshop has resulted in spurt of a new spirit for phytosociological research and a set of new initiatives have been defined. Among those, there was an aim to develop a National Vegetation Databank—the ‘VegEgypt’, a National Vegetation Map and a series of studies dealing with the major phytogeographical regions of Egypt. The present study on vegetation of the Sinai desert must be seen in this context (El-Sheikh and Hatim 2009).

To answer questions with regard to the effects on biodiversity by ongoing changes in land-use and climate, there is an urgent need for adequate data on the species composition of ecosystems. This refers to all major phytogeographical regions, including deserts. For the Sinai desert, one of the major phytogeographical regions in Egypt, even though several vegetation surveys have been carried out (e.g. Migahid et al. 1959; Ahmed 1983; Fayed et al. 2004; Shaltout et al. 2004), not all areas have been exhaustively investigated, and there is no overview of the existing vegetation data, and the whatever data are available are not provided in a standardized format.

The present study includes three goals: (1) collection of all available published and unpublished vegetation survey data of Sinai, for building vegetation database, (2) field vegetation survey covering areas which were not covered in the earlier studies to fill the gaps in data of the previous studies, and (3) analysis of the inventories to provide an overview of the plant communities of Sinai region.

2 Materials and methods

2.1 Study site

Sinai Peninsula is a triangular plateau in the northeast of Egypt with its apex in the south at Ras Muhammad, where the eastern coast of Suez Gulf meets western coast of Aqaba Gulf. Its base, in the north, is along the Mediterranean Sea. The area of Sinai Peninsula (61,000 km2) approximates 6 % of Egypt. More than half of the study area extends over the peninsula included between the Gulfs of Aqaba and Suez. The core of the peninsula, situated near its southern end, consists of an intricate complex of high and very rugged igneous and metamorphic mountains (Fig. 1). The northern two-thirds of the peninsula are occupied by a great northward-draining limestone plateau which rises from the Mediterranean coast, extends southwards and terminates in a high escarpment on the northern flanks of the great igneous core (Said 1962).

Fig. 1
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The main geographical features of the Sinai Peninsula (after Abu Al-Izz 1971)

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Sinai is situated in the extreme northeast of Africa, thus it belongs climatically to the dry province. According to Ayyad and Ghabbour (1986), Sinai Peninsula can be divided into two climatic zones: arid and hyperarid. The arid zone includes the northern region where the area is hot in summer, mild weather in winter with intermittent rainfall. According to UNESCO/FAO Map (1963), this zone is divided into two provinces: (1) the coastal belt province under the maritime influence of the Mediterranean Sea with a relatively shorter dry period, and (2) the inland province with a relatively longer dry period. The hyper-arid zone covers the central and southern regions. It is also distinguished into two provinces: (1) hyper-arid province with hot summer, mild winter and rainfall. It includes central Sinai or the El-Tih plateau together with the western and eastern coasts of the Gulfs of Aqaba and Suez; (2) hyperarid province with cool winter and hot summer located around the summits of the Sinai Mountains (Zahran and Willis 2009).

According to Takhtajan et al. (1986), the Sinai Peninsula lies in the Saharo-Arabian Region, but this classification neglects the presence of Mediterranean coastal part of Sinai. According to Zahran and Willis (2009), Sinai Peninsula stands in the middle of three provinces, Saharo-Sindian Province, Irano-Turanian Province and the Mediterranean region. Saharo-Sindian Province encompasses the great desert from the Atlantic coast of Morocco to the deserts of South Afghanistan. The air is dry, temperatures are high, rainfall is low, salty ground is abundant, less species diversity, abundance, and uniform vegetation (Zahran and Willis 2009).

2.2 Sampled collections

Sinai Peninsula has always attracted the attention of many explorers and botanists since seventeenth century and even earlier. Täckholm (1932) and Zohary (1935) gave accounts of important contributions on the flora of Sinai. Batanouny (1985) presented a full report describing the activities of explorers and botanists in the peninsula from 1761 to the present. Among those, Delile who visited Egypt in 1798–1801 under the command of Napoleon I and later published an Histoire Naturelle in two volumes (Delile 1809–1812), and Fresenius (1834) whose Beitrage zur Flora von Aegypten und Arabien can be considered as the first account of the flora of Sinai.

The first step in our study was an inventory and review of available literature and non-published data of the vegetation of the Sinai Peninsula. This was serving two objectives: (1) collection of published and unpublished data for building the Sinai vegetation database, and (2) a general idea of the diversity and main vegetation zones in the area. The data collection was mainly based on studies of various persons mentioned in (Table 1).

Table 1 Sources of data collected and number of relevés in the database
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The species nomenclature follows the latest check list of Egypt flora (Boulos 2009). For the input of vegetation plot data, the computer package Turboveg was used, which was designed within the context of the national vegetation classification of the Netherlands, first as a DOS-version, in 1996 followed by Turboveg for Windows. This software comprises a comprehensive database management system for the input, processing and presentation of data (Hennekens and Schaminée 2001).

Many data records lacked some information like coordinates, altitude, relevé area, and habitat type. The majority of the records belong to the southern Sinai due to the importance of this region as a center of medicinal and endemic plants. This database is the first of its kind amining to use it as a nucleus for the Egyptian National Vegetation Database. The database entering in Turboveg software is demonstrated as a flow chart (Fig. 2).

Fig. 2
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Flow chart of the database handling using Turboveg

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After investigating the available data it was obvious that there are many places not well represented in the database, these places were mainly in the Middle and Northern regions of Sinai. We described 182 phytosociological relevés in the under sampled areas between March 2010 and September 2010 according to the Braun-Blanquet approach (1928; Westhoff and van der Maarel 1973). The selection of these relevés was based on the variation of the geomorphology, habitats and vegetation types of the under sampled areas, and were added to the database. Herbarium sheets were made for them and were added to the Herbarium collection of the Botany Department of Faculty of Science, Tanta University (TANE). Not all places are covered since some places still require detailed descriptions.

2.3 Data analysis

The whole database was analyzed during a three-month stay by University of Wageningen in The Netherlands (2010–2011). Software packages were used for the analysis, Turboveg program was used for the storing and managing of the database (Hennekens and Schaminée 2001), and Juice program was used for the classification and additional analysis of the data (Tichý 2002). The data analysis was mainly in two trends of multivariate analysis that were applied in the present study, classification and ordination. Both trends have their merits in helping to understand the vegetation and environmental phenomena. The Two-Way Indicator Species Analysis (TWINSPAN), as a classification technique (Hill 1979a), and Detrended Correspondence Analysis (DECORANA), as an ordination technique (Hill 1979b), were applied to the floristic composition of the 816 relevés recorded. Then, 12 vegetation types (i.e. alliances) at level 3 of the TWINSPAN classification and 21 vegetation groups (i.e. associations) at level 6 were identified in the study area, according to (Jennings et al. 2009).

2.4 Diversity indices

Some of the diversity indices were calculated for the vegetation in relation to the plant associations and habitats. Such indices could be considered as macroscopic properties of communities encompassing both the number of species present and the distribution of the individuals between them (De Jong 1975). Species richness (alpha diversity) for each plant associations and habitat was calculated as the average number of species per relevé. Species turnover (beta diversity) could be defined as the extent of species replacement or biotic change along environmental gradients (Whittaker 1972). It is calculated as the ratio between the total number of species recorded in a certain plant associations or habitat and its alpha diversity (Wilson and Shmida 1984).

2.5 Conservation measures

The critical conditions of survival of the species were assigned as a result of the observed habitat’s loss, ecological imbalance or commercial exploitation during the last decades. Conservation categories of the plants represented in the flora of the study area were collected from EL-Hadidi and Hosni (2000) and Boulos (2009) as shown in (Table 2).

Table 2 IUCN conservation categories of the threatened species
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2.6 Endemic and sub-endemic species

Endemics are usually rare and restricted to rather small geographical regions, so they deserve special attention for their conservation (Boulos 1997). The Endemic and sub-endemic species in the study area are indicated following from Täckholm (1974), and Boulos (1997, 1999, 2000, 2002, 2005, 2009).

3 Results

3.1 Floristic diversity

Four hundred and ninety six species belonging to 69 families were recorded in the present study. Pteridophyta is represented by 2 families, 2 genera and 2 species; while Gymnospermae is represented by 2 families, 2 genera, 5 species, and 1 sub-species. Dicotyledoneae are represented by 57 families, 229 genera, 405 species, and 77 sub-species. The most represented families of them are Compositae (Asteraceae) (63 species), Leguminosae (Fabaceae) (45 species), Chenopodiaceae (30 species), Caryophyllaceae (24 species), Labiatae (Lamiaceae) (23 species), Crucifereae (Brassicaceae) (20 species), and Zygophyllaceae (15 species). Two families are represented by 14 species, one family by 11 species, three families by 9 species, four families by 8 species, one family by 7 species, two families by 6 species, three families by 5 species, and two families by 4 species. Monocotyledoneae are represented by 8 families, 48 genera, 67 species, and 5 sub-species (Table 3). The most represented family is Gramineae (Poaceae) (46 species), while Cyperaceae has 7 species and Juncaceae has 6 species.

Table 3 Representation of families with actual number of species ≥6 in the flora of Sinai
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3.2 Life forms

The herb layer is the most represented life form (71.7 % of the total species). The low shrub layer was represented by 23.4 %, while the middle tree layer was represented by 3.2 % of the total species. The low tree layer (0.8 %), high shrub layer (0.6 %), high tree layer (0.2 %), and moss layer (0.2 %) are the less represented life forms (Fig. 3).

Fig. 3
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Percentage of the life forms of the recorded species in Sinai

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3.3 Phytosociological approach

3.3.1 Vegetation classification

The analysis of the matrix of 816 relevés and 496 species (cover estimates) according to TWINSPAN led to identify 21 groups (i.e. associations) at level six and 12 vegetation types (i.e. alliances) at level 3 (Fig. 4). According to (Jennings et al. 2009), the association is the primary unit of vegetation, reflecting patterns of plant species occurrence and frequency. The alliance is the next broader unit of vegetation and is composed of one to many associations. Each association and each alliance is named according to the dominant species that have the highest presence percentages. Their segregation along the first two axes of DECORANA is presented in Fig. 4.

Fig. 4
figure 4

TWINSPAN classification (a) and DECORANA ordination (b) of the 21 vegetation associations identified in the Sinai

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  • Associations

Three associations were represented in Northern, Middle and Southern Sinai:

  • Halocnemum strobilaceum ass. (25 relevés) with characteristic species Zygophyllum album, Nitraria retusa and Halocnemum strobilaceum (1);

  • Panicum turgidum ass. (49 relevés) with characteristic species Panicum turgidum, Stipagrostis scoparia and Cornulaca monacantha (4);

  • and Retama raetam subsp. raetam ass. (43 relevés) with characteristic species Retama raetam subsp. raetam, Hyoscyamus boveanus and Aristida adscensionis (16).

  • Another three associations were represented in Northern and Southern Sinai:

  • Salvadora persica ass. (27 relevés) with characteristic species Zygophyllum album, Nitraria retusa and Salvadora persica (2);

  • Moricandia sinaica ass. (31 relevés) with characteristic species Moricandia sinaica, Juniperus phoenicea and Asparagus stipularis (17);

  • and Mentha longifolia subsp. typhoides ass. (35 relevés) with characteristic species Mentha longifoli a subsp. typhoides, Echinops glaberrimus and Launaea spinosa (18).

Eight associations were represented in Middle and Southern Sinai:

  • Tamarix nilotica ass. (25 relevés) with characteristic species Tamarix nilotica, Asphodelus fistulosus and Fagonia thebaica (5);

  • Haloxylon salicornicum ass. (38 relevés) with characteristic species Haloxylon salicornicum, Ephedra alata and Reaumuria hirtella var. hirtella (6);

  • Zygophyllum coccineum ass. (61 relevés) with characteristic species Zygophyllum coccineum, Fagonia mollis var. hispida and Fagonia bruguieri (7);

  • Atriplex halimus ass. (48 relevés) with characteristic species Atriplex halimus, Pergularia tomentosa and Plantago lagopus (8);

  • Indigofera arabica ass. (31 relevés) with characteristic species Indigofera arabica, Acacia tortilis subsp. raddiana and Aerva lanata (10);

  • Pulicaria undulata subsp. undulata ass. (47 relevés) with characteristic species Pulicaria undulata subsp. undulata, Zygophyllum simplex and Cleome droserifolia (11);

  • Artemisia judaica ass. (39 relevés) with characteristic species Artemisia judaica, Schismus barbatus and Cleome amblyocarpa (14); and

  • Fagonia mollis var. mollis ass. (32 relevés) with characteristic species Fagonia mollis var. mollis, Caylusea hexagyna and Trichodesma africanum var. africanum (15).

Seven associations were represented only in Southern Sinai:

  • Convolvulus arvensis ass. (39 relevés) with characteristic species Convolvulus arvensis, Euphorbia peplus and Chenopodium murale (3);

  • Fagonia scabra ass. (32 relevés) with characteristic species Fagonia scabra, Aerva javanica and Tephrosia purpurea subsp. apollinea (9);

  • Centaurea postii ass. (53 relevés) with characteristic species Centaurea postii, Glaucium arabicum, Periploca aphylla subsp. aphylla (12);

  • Aerva javanica var. bovei ass. (26 relevés) with characteristic species Aerva javanica var. bovei, Reseda decursiva and Fagonia arabica var. arabica (13);

  • Achillea fragrantissima ass. (28 relevés) with characteristic species Achillea fragrantissima, Peganum harmala and Centaurea eryngioides (19);

  • Stachys aegyptiaca ass. (52 relevés) with characteristic species Stachys aegyptiaca, Chiliadenus montanus and Matthiola arabica (20); and

  • Tanacetum sinaicum ass. (55 relevés) with characteristic species Tanacetum sinaicum, Phlomis aurea and Teucrium polium (21).

  • Alliances

Twelve alliances were resulted at level 3 and named after their characteristic species as follows:

  • (I) in the salt marshes, and sand flats and hummocks: Zygophyllum album–Zygophyllum coccineum all.

  • (II) in the gardens, wadi bed, wadi slope, and rocky soil: Convolvulus arvensis all.

  • (III) in the gravel desert, wadi bed, and wadi slope: Haloxylon salicornicum–Artemisia judaica all.

  • (IV) in the sand flats and hummocks, wadi bed, and gardens: Fagonia mollis var. mollis all. and (VIII) Pulicaria undulata subsp. undulata all.

  • (V) in the sand flats and hummocks, gravel desert, and wadi bed: Atriplex halimus all. and (VI) Fagonia scabra all.

  • (VII) in the gravel desert, wadi bed and wadi terraces: Indigofera Arabica all.

  • (IX) in the wadi bed, wadi slope and rocky soil: Moricandia sinaica all. and (X) Mentha longifolia subsp. typhoides all., (XI) Achillea fragrantissima-Stachys aegyptiaca all., (XII) Tanacetum sinaicum all.

3.3.2 Species diversity of the plant associations

The number of relevés supporting the 21 plant associations ranges from 25 in associations 1 and 5–61 in associations 7, while the number of species ranges from 12 in association 5–291 in association 18. The percentage of the number of relevés per association to the total relevés ranges from 3.1 % in associations 1 and 5–7.5 % in association 7. The species richness ranges from 2.2 per stand in association 5 (S.D. = 1.5) to 35.9 per stand in association 18 (S.D. = 12.8). The species turnover ranges from 2 in associations 17–16 in associations 7 (Table 4).

Table 4 Species diversity of the 21 vegetation associations identified
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3.4 Habitat approach

3.4.1 Identified habitats

The diagrammatic biosectors along N–S and W–E directions in Sinai indicate 21 major habitats: 4 in the North, 5 in the Middle and 12 in the South (Fig. 5). The habitats that support the 21 plant associations are indicated in Table 5. Seventeen species occur in more than 50 % of the habitats: Lycium shawii, Zygophyllum album, Nitraria retusa, Zygophyllum simplex, Cornulaca monacantha, Anabasis articulata, Haloxylon salicornicum, Panicum turgidum, Stipagrostis plumosa, Zygophyllum coccineum, Caylusea hexagyna, Fagonia mollis var. mollis, Retama raetam subsp. raetam, Seriphidium herba-alba, Zilla spinosa subsp. spinosa, Fagonia arabica var. arabica and Farsetia aegyptia subsp. aegyptia. The unique species of the major habitats in Sinai are indicated in (Table 6).

Fig. 5
figure 5

Diagrammatic biosectors indicating the main habitats along North–South and West–East directions in Sinai

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Table 5 The supporting habitats of the 21 vegetation associations
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Table 6 The exclusive species of the habitat in Sinai
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The classification of the 21 habitats based on their floristic composition led to identify 4 associations at level 1, 6 at level 2, 7 at level 3, 8 at level 4, 10 at level 5, 11 at level 6, 13 at level 7, 16 at level 8, 19 at level 9, 20 at level 10 and 21 at level 11 (Fig. 6). Their segregation along the first two axes of DECORANA reflects a complex of floristic composition and habitats resulting in formation of 13 habitat types at the level 7 of classification.

Fig. 6
figure 6

TWINSPAN classification (a) and DECORANA ordination (b) of the 21 main habitats identified in the Sinai region based on their floristic composition

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3.4.2 Species diversity of the habitats

The number of surveyed relevés ranged from one in the cave habitat to 140 in the wadi bed, and the species number ranged from 5 in the mangrove habitat to 318 in the wadi slope in Southern Sinai (Table 7). The number of relevés per habitat to the total relevés ranges from 0.1 % in the cave to 17.2 % in the wadi bed; while the number of species per habitat to the total species ranges from 1 % in the mangroves to 64.1 % in the wadi slope. The species richness ranges from 2.3 species per relevé in the mangroves to 23 species per relevé in the wadi slope. Finally the species turnover ranges from 0 in the cave habitat to 12.8 in the wadi slope.

Table 7 Species diversity of the 21 habitats in Sinai, the minimum and maximum values are underlined
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3.5 Conservation measures

Fifty-two threatened species are recorded in the present study, their conservation categories could be arranged descendingly as follows (Fig. 7): 18 endangered species (e.g. Juniperus phoenicea, Ficus carica and Dianthus sinaicus), 17 rare species (e.g. Equisetum ramosissimum, Haloxylon persicum and Hypericum sinaicum), 13 vulnerable species (e.g. Atraphaxis spinosa, Seidlitzia rosmarinus and Zilla spinosa) and 4 indeterminate species (e.g. Cleome droserifolia, Erodium arborescens and Althaea ludwigii). All these species (Table 8) are located in Southern Sinai except Juniperus phoenicea and Callipeltis cucullaris in Northern Sinai, while Zilla spinosa in Middle Sinai.

Fig. 7
figure 7

Conservation categories of the recorded species in Sinai region

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Table 8 Red data list of the plant species recorded in Sinai
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3.6 Endemic and sub-endemic species

Sixteen endemic species were recorded in the present study (Table 9). All the endemic species are located in Southern Sinai, except Plantago sinaica in Middle Sinai. In addition, 20 sub-endemic species were recorded from Egypt and other neighboring countries such as Palestine (12 species), Saudi Arabia (5 species), Libya (2 species) and Sudan (1 species) (Table 10).

Table 9 The endemic species recorded in the study area
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Table 10 The sub-endemic species recorded in the study area
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4 Discussion

The total number of species recorded in the present study is 496 belonging to 281 genera and 69 families. Asteraceae (63 species), Poaceae (46 species) and Fabaceae (45 species) are the dominant families represented together by 154 species which is about 31 % of the total number of the recorded species. This number is closer to 532 species recorded by Hassib (1951), and the other estimates were 942 (Zohary 1935), 1247 (Täckholm 1974), 687 (Abduallah et al. 1984), 886 (Danin 1972), 984 (El-Hadidi et al. 1991) and 1262 (Boulos 1995). The dominant families as recorded in the present study agree with the findings by Ayyad et al. (2000) and Moustafa and Zaghloul (1996).

The herb layer is the most represented life form (71.7 % of the total species), followed by the low shrub layer (23.4 %). The low tree layer (0.8 %), high shrub layer (0.6 %), high tree layer (0.2 %) and moss layer (0.2 %) are the less represented forms. This indicates that the therophytes (mainly herbs) are the most frequent life forms followed by chamaephytes (low shrubs). Phanerophytes (shrubs and trees) are the less frequent life forms; these findings are similar to that of Hassib (1951).

There are three main reasons why ecologists are interested in ecological diversity and its measurement, (1) despite changing fashions and preoccupations, diversity has remained as a central theme in ecology, (2) greater measures of diversity are frequently seen as indicators of better ecological systems, and (3) diversity has become an important measure for the evolution of the ecosystem. That is because diversity consists of not one but two components. In the first category, number of species referred to as species richness and second—the relative abundance of species. Species diversity increases as the number of species per sample increases, and the abundance of species within a sample become even (Pielou 1969).

Zohary (1973) concluded that moisture, in the form of rainfall, is the most decisive factor controlling plant distribution and life form in arid lands. The limiting factors that affect the species diversity in Sinai are water availability and landform types (Danin 1983). The present study showed that plant associations that inhabit the sand formations (i.e. sand dunes and sand flats and hummocks) have the lowest species richness and species turnover; it is obviously because of the openness of such habitats and the scarcity of rainfall which is a main source for water supply. On the other hand, plant associations that inhabit rocky soil, wadi bed and wadi slope, have the highest species richness and species turnover; it is obviously because such habitats have more abundant water supply. Rocky soils and wadi slopes are characterized by wadi filling materials, sediments and a high proportion of gravel and fine grains in the soil pockets that can trap water (Ayyad et al. 2000).

According to TWINSPAN technique, twenty-one plant associations were generated in the present study. Their ordination using DECORANA technique represents complex plant associations of floristic composition and habitats. Halocnemum strobilaceum association, which inhabits salt marshes, sand formations and mangroves, is similar to those reported by Migahid et al. (1959), Gibali (1988), Hussein (1988), El-Demerdash et al. (1996) and Marie (2000). Salvadora persica association, which inhabits salt marshes, sand formations and water springs is similar to those reported by Helmy et al. (1996) and El-Demerdash et al. (1996). Convolvulus arvensis association, which inhabits gardens, rocky soil, wadi bed, and wadi slope is restricted to the habitats under agricultural activities. Panicum turgidum association, which inhabits salt marshes, sand dunes, sand flats and hummocks, gardens, gravel desert, mangroves, rocky soil, wadi bed, wadi slope, wadi terraces, and water springs, is similar to those reported by Ahmed (1983), Danin (1983), El-Demerdash et al. (1996), Gibali (1988) and Marie (2000). Tamarix nilotica association, which inhabits salt marshes, sand dunes and sand flats, and hummocks is similar to those reported by Migahid et al. (1959), Danin (1983), El-Kady and El-Shourbagy (1994), Marie (2000), Abd El-Ghani and Amer (2003) and Morsy et al. (2010). Haloxylon salicornicum association, which inhabits sand formations, gardens, gravel desert, rocky soil, wadi bed, and wadi slope is similar to those reported by Migahid et al. (1959), El-Kady et al. (1998), Abd El-Wahab et al. (2006) and Morsy et al. (2010).

Zygophyllum coccineum association, which inhabits salt marshes, sand dunes, sand flats and hummocks, gardens, gravel desert, mangroves, wadi bed, wadi slope, wadi terraces, and water springs, is similar to those reported by Ahmed (1983), Danin (1983), El-Demerdash et al. (1996), El-Kady et al. (1998), Marie (2000), Abd El-Wahab et al. (2006) and Morsy et al. (2010). The association of Atriplex halimus, which inhabits salt marshes, sand flats and hummocks, gardens, gravel desert, wadi bed, wadi slope, wadi terraces, and water springs is similar to that reported by Marie (2000). The associations of Fagonia scabra which inhabits sand formations, gardens, gravel desert, rocky soil, wadi bed, wadi slope, and wadi terraces; Centaurea postii which inhabits rocky soil, wadi bed and wadi slope; Aerva javanica var. bovei which inhabits gravel desert, rocky soil and wadi bed; and that of Indigofera arabica which inhabits gravel desert, rocky soil, wadi bed, wadi slope, wadi terraces, are not reported in the other studies.

Association of Pulicaria undulata subsp. Undulata, which inhabits rocky soil, sand flats and hummocks, wadi bed, wadi slope is similar to that reported by El-Demerdash et al. (1996). The association of Artemisia judaica, which inhabits gravel desert, sand dunes, gardens, rocky soil, wadi bed, wadi slope, and cave is similar to those reported by Migahid et al. (1959), Danin (1983), Moustafa and Zaghloul (1996), Moustafa (2000) and Abd El-Wahab et al. (2006).

Association of Fagonia mollis var. mollis, which inhabits gravel desert, sand dunes, gardens, rocky soil, wadi bed, wadi slope, and wadi terraces is similar to those reported by Danin (1983), Moustafa and Zaghloul (1996), Ayyad et al. (2000) and Moustafa (2000). Association of Retama raetam subsp. Raetam, which inhabits gravel desert, sand formations, rocky soil, wadi bed, and wadi slope is similar to those reported by Migahid et al. (1959), Danin (1983), Marie (2000), Abd El-Wahab et al. (2006) and Morsy (2010). Association of Moricandia sinaica, which inhabits rocky soil is similar to those reported by Danin (1983) and El-Bana et al. (2010). The association of Mentha longifolia subsp. Typhoides, which inhabits gardens, rocky soil, wadi bed, and wadi slope is similar to those reported by Moustafa and Zaghloul (1996) and Abd El-Wahab et al. (2006).

Association of Achillea fragrantissima, which inhabits gravel desert, rocky soil, wadi terraces, wadi bed, and wadi slope is similar to those reported by Migahid et al. (1959), Danin (1983), Moustafa and Zaghloul (1996) and Marie (2000). The association of Stachys aegyptiaca, which inhabits rocky soil and wadi slope is similar to those reported by Danin (1983), Moustafa and Zaghloul (1996), Ayyad et al. (2000) and Abd El-Wahab et al. (2006). Association of Tanacetum sinaicum, which inhabits gravel desert, rocky soil, wadi bed, and wadi slope is similar to those reported by Danin (1983), Moustafa and Zaghloul (1996), Moustafa (2000), Moustafa et al. (2000) and Abd El-Wahab et al. (2006).

Fifty-two species (10.7 % of the total species) recorded in the present study are threatened, eighteen species (3.6 % of the total species) are endangered, seventeen species (3.4 % of the total species) are rare, thirteen species (2.6 % of the total species) are vulnerable, and four species (1 % of the total species) are indeterminate. It is noted that the large majority of these species are located in Southern Sinai. In general, threats to the world’s plants continue to increase as a result of human activities, e.g. poor land management, over collection, habitat loss, presence of invasive species, and climate change. Most studies suggest that the rate at which plant species are being lost, or at least decreased in number, is faster than the speed at which scientists; land managers, policy makers and others can or will respond. Botanical gardens are uniquely positioned to play a leading role in plant conservation by creating public awareness of the importance of plants.

The percentage of endemic species is highest in insular floras (Carlquist 1974; Bramwell 1979), peninsulas and mountain chains (Hedberg 1969; Davis 1971; Rodgers and Homewood 1982; Strid 1986). In North Africa, the highest species endemism is in Morocco (17 %), followed by Algeria (7 0.9 %), Libya (7 0.3 %), Egypt (3.5 %) and Tunisia (1.7 %) Boulos (1997). Out of 60 endemic species in Egypt, Sinai Peninsula has about 39 (65 % of the Egyptian endemic species) in its southern mountainous region (Boulos 2009). Sixteen endemics were recorded in the present study area which formed 41 % of the endemic species of Sinai and 26.7 % of the endemic species of Egypt (see Boulos 2009). On the other hand, out of 93 sub-endemic species of Egypt (Boulos 2009), 20 sub-endemics were recorded in the present study which formed 21.5 % of the total sub-endemics of Egypt. They are restricted to Egypt and other neighboring countries such as Palestine (12 species), Saudi Arabia (5 species), Libya (2 species), and Sudan (1 species).