Natural plant species inventory of hotspot areas in Arabian Peninsula: Southwest Al-Baha region, Saudi Arabia.

Plant hotspot areas are the areas that are very rich in plant species diversity. These areas have a priority for conservation. To highlight the plant diversity for nature conservation purposes a case study in Al Baha region, Saudi Arabia is presented, in which the importance of the natural vegetation and flora of one of the hotspot areas of Saudi Arabia is evaluated through the explanation of its natural plant species. A survey study has been conducted in an area of 167.6 km2, a 97 sample each with 20X20 m were laid out covering the whole ecological zones of the study site. Data of flora, vegetation cover and topography were gathered from each sample site. The study revealed about 319 plant species belonging to 228 genera and 75 families. Two species were found endemic to Saudi Arabia, 14 were endemics to Arabian Peninsula, and five were regional endemics that are only found in East Africa and Arabian Peninsula, while 39 species are rare and endangered.

Introduction

The Mountains in southwestern Saudi Arabia (i.e. Sarawat), are considered as one of the richest biodiversity areas in the Arabian Peninsula and comprises a large number of endemic, endangered and threatened plant species (Abuzinada et al., 2005, Qushas, 2007). Biodiversity hotspots play a leading role in international and national nature conservation strategies (Hobohm et al., 2016). The study area is located on the Sarawat Mountains and within The Eastern Afromontane Hotspot area (Mallon, 2011). This area has rich biodiversity and is considered as one of the richest plant diversity areas in the Arabian Peninsula (Al-Aklabi et al., 2016, Al-Zandi et al., 2018). It also supports high rates of endemism, large numbers of rare species and a few endangered plant species with restricted distributions on inaccessible slopes facing the Red Sea (Al-Khulaidi et al. 2018). Some of the monotypic trees can be remnants of past forests and ancient heritage (Aronson et al. 2016), where many forest elements have destroyed and declined due to climate change and human activities.

Many studies on plant diversity of ecological sites in Saudi Arabia were conducted (e.g. Ghazanfar and Fisher, 1998, Hegazy et al., 1998, Chaudhary and Al-Jowaid, 1999, Hall et al., 2011, El-Sheikh, 2013, Alatar et al., 2015). The outcome of some of them (e.g. Collenette, 1985, Collenette, 1999, Thomas et al., 2017) takes into account the endemism and endangered plant species. However, a few of them highlighted the important areas of plant diversity in Saudi Arabia (e.g. Al-Abbasi et al., 2010, Llewellyn et al., 2010, Hall et al., 2010, Hall et al., 2011, Thomas et al., 2017).

The flora and the vegetation of the study area are a mixture of different climatic conditions and of different elements of Saharo-Arabian or Saharo-Sindian, Sudanian region, and Mediterranean region (Al-Khulaidi, 2013, Al-Aklabi et al., 2016). This due to a variation in rainfall from dry at low altitude and relatively wet at high altitude and due to different types of landscape and altitude ranges from 650 to 2350 m. (Fig. 2). Few vegetation studies were conducted in Al-Baha region covering part of the study area (Al-Aklabi et al., 2016, Al-Zandi et al., 2018, Al-Khulaidi et al., 2018a, Al-Robai et al., 2019).

Fig. 2

The altitude of the study area.

In this study, we aim to highlight the important plant area in Albaha region. Our research will include an inventory for the plant diversity of the targeted study area. In addition, the study aims to highlight the hotspot areas that have the highest plant species richness and further plant biodiversity among the studied zones.

Materials and methods

The study area

The study was conducted in the period from April 2017 to July 2018, near Baljurashi city in the southwest of Al-Baha region, (between 19.41: 19.50 North and between 41.29 and 41.44 East), The study area covers the ecological zones located around Hawala, Jabal Uthrob, Al Abna and Huzna areas (Fig. 1). These areas stretch parallel to Tihamah plain and extend for approximately 68 km. from Assollubat fault in the south to Huznah escarpment in the north. The altitude ranges between 300 and 2350 m above sea level (masl). The slopes and the plateaus directed sharply to Tihamah plain, and become lower and gradually slope eastward. Deep wadis and drainage lines cut the mountains, and flow toward the Tihama foothills. Tihamah foothills area border the eastern and western sides of Jabal Uthrub escapement, which is covered by rocks, gravels, and rock outcrops.

Fig. 1

The location of the study area.

In general, the Arabian Shield, where the study was conducted is composed of a stable Craton of predominantly late Precambrian metavolcanic and plutonic rocks. Its surface is composed of around 50% plutonic rocks, and 50% volcanic sedimentary rocks. Granit consists of about 70% of plutonic rocks. Most rocks in Hawalah area are Amphibolite, Biotite, Tonalite, Gabbro, Andesite, and Granite (Brown et al., 1989).

The landscape variation strongly influences the flora, composition, structure of the vegetation communities and vegetation types. The variation of landscape in particular that facing the west and effected by fog provides a vegetation edge microclimate ecosystem (Young and Mitchell, 1994), which supports unique flora, vegetation composition and structure with endemic, rare plant species. The altitude of the study area ranges between 600 and 2240 masl (Fig. 2). The terraces are confined nearly to the high altitude areas, most of these terraces are neglected for years, and as a result, they became covered by natural vegetation dominated by Vachellia origena (=Acacia origena) with associated species such as Juniperus procera, Asphodelus fistulosus, Achillea biebersteinii, Nepeta deflersiana, Tripteris vaillantii, Hyparrhenia hirta, Eragrostis papposa and others.

The Geographic Information System GIS (Arc Map software) was used to generate maps of the endemic, near-endemic, rare, endangered species, plant density and plant richness throughout the study area. Diversity indices were applied using a MultiVariate Statistical Package (MVSP) software and by using Simpson's and Shannon's method to identify the more diverse sample sites. The total number of samples was 97 samples, each with a size of 20X20 m. and dispersed randomly in an area of 167.6 km 2, with the assurance that the samples covered all ecological zones and topographic units of the study area.

Plant population parameters

Density: Number of individuals of each species counted in each sample site

The numbers of individuals of each species in each site were then converted to a number of individuals per hectare. This is achieved by dividing the total number of individuals by the total areas surveyed in the different landforms.

Frequency: Frequency was calculated by dividing the number of plots in which a species occurs into the total number of plots sampled

Al-Zandi et al, 2018

Endemism: The endemic plant species is defined for this study as the plant that only occurs in Saudi Arabia; the near-endemic species are those that occur only in the Arabian Peninsula (mainly Saudi Arabia and Yemen)

The distribution of endemic and near-endemic species are based on Collenette 1985); Wood, 1997, Al-Khulaidi, 2013.). The Regional endemics in the study area are the plants that occur only in the Arabian Peninsula and East Africa (Somalia, Ethiopia, Djibouti, Sudan, Kenya, Uganda, Tanzania) (Fig. 3). The distribution of regional endemic plants was based on information from (Thulin 1993- Volume 1, 2, 3 and 4, Rendle, 1916, Edwards et al., 2000, Hedberg and Edwards, 1989 as well as Wood (1997).

Fig. 3

Eastern Africa, 1 Somalia, 2 Ethiopia, 3 Djibouti, 4 Sudan (North & South), 5 Uganda, 6 Kenya, 7 Tanzania.

Results

In total, 319 plant species belonging to 75 families and 228 genera were found in the surveyed area (Appendix1). Two species are endemic to Saudi Arabia, 14 are endemic to Arabian, 5 regional endemic only found in East Africa and Arabian Peninsula and 39 are rare and endangered, most of them were concentrated around Jabal Uthrub, Hawala, and at the top of Al Abna and Huzna descents (Fig. 4)

Fig. 4

The concentration of endemic, rare and endangered plant species.

The family Asteraceae is represented by the highest number of species (35 species) followed by the Poaceae (27 species), Lamiaceae (19 species), Fabaceae (15 species), Acanthaceae (12 species), Apocynacaea (11 species), Euphorbiaceae and Mimosaceae (10 species) (Fig. 5). The previous prominent eight families together contribute 139 plant species (44% of the overall total species). Twenty-eight families (29% of the overall total) are represented by only a single species, with the most common ones being Barbeyaceae (Barbeya oleoides), Ericaceae (Erica arborea).

Fig. 5

High represented families with their percentage.

Frequency

About 82% of the total plant species were categorized in the lowest frequency class, whereas 11% of the plants were distributed in the second frequency class. With a frequency of 49%, Juniperus procera is the most frequent species followed by Maytenus parviflora (41%) and Senegalia asak (=Acacia asak) with frequency (39%). Most abundant species with a frequency of more than 20% are shown in Fig. 6. Many species were very rare and endangered, with a frequency between 1 and 2%. The most important and rarest species were Boscia angustifolia, Periplocha aphylla, Commiphora kua, Euphorbia cuneata, Kleinia odora, Psitacia falcata, Salvia merjamie, Teclea nobilis, and Jasminum fluminense with a frequency 1% (Table 1).

Fig. 6

Most abundant species with their percentage frequency.

Table 1

Rare and endangered plant species, with a frequency between 1 and than 2%.

Plant name	Freq.%	Plant name	Freq.%	Plant name	Freq.%
Acacia oerfota (=Vachellia oerfota)	2	Lycium shawii	2	Boscia angustifolia	1
Aloe castelorum	2	Monolluma quadrangula	2	Periplocha aphylla	1
Barleria acanthoides	2	Pentas lanceolata	2	Commiphora kua	1
Caralluma wissmani	2	Phoenix caespitosa	2	Euphorbia cuneata	1
Celtis africana	2	Pulicaria petiolaris	2	Kleinia odora	1
Cordia monoica	2	Rhamnus staddo	2	Psitacia falcata	1
Cynoglossum bottae	2	Silene yemensis	2	Salvia merjamie	1
Dobera glabra	2	Tamarix nilotica	2	Teclea nobilis	1
Euclea racemosa	2	Grewia velutina	1	Jasminum fluminense	1
Leucas alba	2	Barleria hochstetteri	1

Endemism

The study area contains a remarkable number of endemic plant species. These are estimated to be about 16% of the vascular flora of the study area, in which endemic (two species), near endemic (14 species) and regional endemic (34 species) (Table 2). Fig. 3 shows the distribution of endemism, rare and endangered plant species of the study area.

Table 2

Endemic, near endemic and regional endemic of the study area.

Plant name	Endemism	plant name	Endemism	plant name	Endemism
Aloe pseudorubroviolacea	*	Felicia abyssinica	***	Felicia dentata	***
Plectranthus asirensis	*	Acacia etbaica (=Vachellia etbaica)	***	Grewia velutina	***
Acacia johnwodii (=Vachellia johnwoodi)	**	Acacia hamulosa (=Senegalia hamulosa)	***	Kickxia pseudoscoparia	***
Aloe castelorum	**	Acacia origena (=Vachellia origena)	***	Kleinia odora	***
Barleria bispinosa	**	Anisotes trisulcus	***	Lavandula atriplicifolia	***
Centaurothamnus maximus	**	Barbeya oleoides	***	Lavandula pubescens	***
Crinum album	**	Buddleja polystachya	***	Minuartia filifolia	***
Cynoglossum bottae	**	Caralluma retrospiciens	***	Phoenix caespitosa	***
Gymnosporia parviflora	**	Carissa spinarum	***	Pistacia falcata	***
Leucas alba	**	Cometes abyssinica	***	Pulicaria schimperi	***
Monolluma quadrangula	**	Commiphora gileadensis	***	Searsia retinorrhoea	***
Nepeta deflersiana	**	Commiphora kataf	***	Rumex nervosus	***
Orbea wissmannii var. eremastrum	**	Commiphora kua	***	Seddera arabica	***
Phragmanthera austroarabica	**	Commiphora myrrha	***	Silene yemensis	***
Picris scabra	**	Cordia monoica	***	Solanum schimperianum	***
Teucrium yemense	**	Cyphostemma digitatum	***	Triumfetta flavescens	***
Acacia asak (=Senegalia asak)	***	Dorycnopsis abyssinica	***

KEY Endemism.

* Endemic, ** near endemic, *** regional endemic found in Eritrea, Djibouti, Ethiopia, Sudan, Kenya, Tanzania.

Plant density

The Majority of high-density plants were grasses. These grasses are confined mainly to high altitude areas namely Hyparrhenia hirta and Themeda triandra. Further annual species such as Asphodelus fistulosus and Osteospermum vaillantii were also recorded as high-density species; both species appear along road margins and disturbed sites in the summertime. Among trees, Juniperus procera was a high-density tree and forms woodland of varies vegetation and structure types (Fig. 7).

Fig. 7

Most density species with their density per hectare.

Plant diversity

The most diverse sample sites were: 371, 367, 420 and 423 (Table 3 & Fig. 8). These sample sites were located on the high-altitude areas facing mainly South and South West such as the top of Al Abna descent and on Jabal Uthrub (Hawala).

Table 3

The most diverse sample sites according to Shannon's and Simpson's methods.

Shannon's method				Simpson's method
Log base e				Log base e
Index	Sample	Evenness	Num.Spec.	Index	Sample	Evenness	Num. Spec.
361	371	0.91	53	0.96	371	0.98	53
346	367	0.91	45	0.95	367	0.98	45
333	420	0.88	44	0.95	420	0.97	44
333	423	0.89	43	0.95	423	0.97	43

Fig. 8

The most diverse sample sites are around Hawala and at the top of Al Abna descent.

Discussion

There are 29 rare and endangered plant species in the study area, with a frequency of less than 2% (Table 1). Many plant species in the world are threatened with extinction due to climate change and intensive human activities (Chaudhary and Khan, 2010). A recent study estimates 46 rare and endangered plant species in Al Baha region (Al-Khulaidi et al. 2018b)., Species richness, endemism, or rarity are paramount criteria in selecting important plant areas (IPAs) for conservation strategies (Sánchez de Dios et al., 2017), single plant families can be worth to adding them as one criterion in selecting IPA. Two rare species with single plant families Barbeya oleoides and Erica arborea are found in the study area (Fig. 9).

Fig. 9

Rare species representing a family with a single species. The latitude and altitude points and the scale are for enlarged map.

The topographic factor in some areas, especially those facing the Red Sea, such as areas that located around Hawala, Jabal Uthrum (East) as well as at the top of Al Abna descent and around Huzna village (West), where there are waves of fog, helped to enrich these areas with plant diversity (Fig. 10). Generally, these areas are characterized by both a high density of vegetation and a high number of plant species (i.e. species richness). In terms of conservation, these areas have to be protected and managed properly so that their rich plant diversity resources are preserved.

Fig. 10

Number of species (Richness) per sample site (20 by 20 m.) top and density of plant species per km2. Below.

Barbeya oleoides, is found only in 7 locations around Huzna and at the top of Al Abna descent, the most dominants were found between 1454 and 1768 masl, on drainage lines facing South West and North East. The plant is an endemic of the eastern Afromontane escarpment of the Ethiopian plateau, horn of Somalia, Eritrea, between 1200 and 2900 masl (Rendle, 1916, Friis, 1983, Rendle, 1916). Thus, it is forming part of the transition element between Afromontane and Somalia-Masai regions (Hall, 2008), and SW of Arabian Peninsula mountains, between 700 and 2135 masl (Wood, 1997, Collenette, 1985). This species forms a vegetation type with Olea europaea and Juniperus procera on steep to moderate rocky slope and wadis between 1700 and 2065 masl. (Al-Aklabi et al., 2016). This species recorded also at about 1540 masl in Taif region that characterized by monthly temperature ranges from 13.7 °C to 30.9 °C and an annual rainfall of about 208 mm (Ragab, et al, 2005). This rare plant is considered as one of the medicinal plants of Saudi Arabia (Zakaria, 2010).

Furthermore, Barbeya oleoides has been evaluated by the International Union for Conservation of Nature IUCN as Least Concern and is considered a monotypic tree family that is represented by a single genus and single species. Thus, this species is important taxonomically, and in terms of phytogeography and phylogenetic studies (Rana and Ranade, 2009, Sarwar and Araki, 2010). Some of the monotypic trees can be remnants of past forests and ancient heritage (Aronson et al. 2016), where many forest elements have destroyed and declined due to climate change and human activities.

The rare tree Erica arborea is only found in three locations over 2000 m east of the study area (Jabal Uthrub), on habitats of rock outcrops and with relatively deep soil terraces facing North West. Studies conducted in the region considered this species as one of the rare and endangered taxa (Al-Khulaidi, 2018a; Al-Khulaidi, et al., 2016). According to IUCN categories, the species is considered as Least Concern (Harvey-Brown and Barstow, 2017, Rivers et al., 2019). The plant is native to the Mediterranean, Tropical African Mountains, and Arabian Peninsula (Harvey-Brown and Barstow, 2017). The plant forms a community on mountains with loam; moderate fine granular located between 2800 and approximately 3250 masl South-eastern Highlands of Ethiopia (Yimer, 2007). The plant forms a community in Mediterranean regions of Turkey, where the temperature ranges between 14 and 18 °C with high humidity in summers (Yildirim and Yilmaz, 2005), and ranges in altitudes from 660 to 820 masl, and slope gradient is between 14 and 55%. And in southwest Sardinia where the predominant soils are Leptosols, with average annual rainfall 1056–1072 mm, and average annual temperature in the area 13 °C (Vacca, 2017). Generally, the plant grows and forms communities in areas with high rains and low temperatures in the world, such as the Mediterranean and East Africa regions.

Teclea nobilis, Boscia angustifolia are remarkable species found only in East Africa, Saudi Arabia and Yemen (Thulin 2008). Both are very rare species with a single tree in the habitat (i.e., the study area), the first only seen at 1734 masl, on drainage line facing SW, while the latter is only seen in two locations, inaccessible rocky slope between altitudes 900 and 1650 masl. The two species generally are rare in Al Baha region (Al-Khulaidi et al., 2018a) (Fig. 11). The tree Faidherbia albida is only seen in one location, this rare tree is considered as one of the enigmatic old tree species of great cultural significance in the Middle East (Aronson et al. 2016).

Fig. 11

The distribution of Teclea nobilis, Boscia angustifolia.

Still few rare plant species need to be investigated in detail. These rare and remarkable plant species need taxonomic evaluation, documentation, and conservation, and also need special attention from the preservation and conservation points of view, the extinction of these species, would represent a big loss of plant diversity. The rarity of this plant may be due to the low rain and fog. However, these rare trees may have been introduced in the past, but have not spread, and have thus remained isolated (Rana, and Ranade 2009).

Declaration of Competing Interest

The authors declared that there is no conflict of interest.

Plant name	Frequency %	density/ha	Relative density	Relative frequency	plant name	Frequency %	density/ha	Relative density	Relative frequency
Abutilon fruticosum	7.2	9.5	0.240	0.354	Hibiscus micranthus	2.1	0.5	0.013	0.101
Abutilon sp.	6.2	8.8	0.221	0.303	Hibiscus vitifolius	3.1	2.1	0.052	0.152
Acalypha fruticosa	9.3	9.8	0.247	0.455	Huernia sp.	1.0	1.3	0.032	0.051
Achillea arabica (=Achillea biebersteinii)	7.2	36.1	0.910	0.354	Hyparrhenia hirta	38.1	273.5	6.895	1.870
Achyranthes aspera	10.3	24.7	0.624	0.505	Hypoestes forskaolii	11.3	61.9	1.560	0.556
Adenium obesum	18.6	10.6	0.266	0.910	Ifloga spicata	3.1	3.6	0.091	0.152
Aerva javanica	27.8	32.0	0.806	1.364	Indigofera sp.	3.1	16.2	0.409	0.152
Aerva lanata	10.3	11.1	0.279	0.505	Indigofera spiniflora	2.1	1.0	0.026	0.101
Aizoon canariense	4.1	7.5	0.188	0.202	Indigofera spinosa	18.6	57.0	1.436	0.910
Aloe castellorum	2.1	4.9	0.123	0.101	Jasminum fluminense	1.0	0.5	0.013	0.051
Aloe pseudorubroviolacea	5.2	7.7	0.195	0.253	Jasminum grandiflorum	20.6	17.5	0.442	1.011
Alyssum desertorum	2.1	1.0	0.026	0.101	Jatropha glauca	2.1	2.8	0.071	0.101
Amaranthus sp.	1.0	0.8	0.019	0.051	Jatropha pelargoniifolia	5.2	2.6	0.065	0.253
Ambrosia maritima	2.1	64.9	1.638	0.101	Juniperus procera	49.5	137.1	3.457	2.426
Ammi majus	2.1	3.4	0.084	0.101	Justicia flava	5.2	4.6	0.117	0.253
Anarrhinum forskaohlii subsp. forskaohlii (=Anarrhinum orientale)	1.0	4.1	0.104	0.051	Justicia odora	1.0	0.5	0.013	0.051
Anchusa ovata	1.0	0.3	0.006	0.051	Kickxia pseudoscoparia	6.2	2.3	0.058	0.303
Andropogon distachyos	12.4	35.1	0.884	0.606	Kleinia odora	1.0	0.3	0.006	0.051
Andropogon sp.	1.0	2.6	0.065	0.051	Lactuca dissecta	2.1	2.1	0.052	0.101
Anisotes trisulcus	17.5	52.6	1.326	0.859	Lamarckia aurea	2.1	18.0	0.455	0.101
Argemone ochroleuca	4.1	6.2	0.156	0.202	Lantana sp.	3.1	1.5	0.039	0.152
Argyrolobium arabicum	6.2	4.4	0.110	0.303	Launea sp.	4.1	1.5	0.039	0.202
Aristida adscensionis	35.1	147.2	3.711	1.718	Lavandula atriplicifolia	2.1	0.5	0.013	0.101
Arthraxon sp.	1.0	0.5	0.013	0.051	Lavandula coronopifolia	4.1	3.1	0.078	0.202
Asparagus africanus	1.0	0.5	0.013	0.051	Lavandula dentata	19.6	37.6	0.949	0.960
Asphodelus fistulosus	10.3	114.2	2.879	0.505	Lavandula pubescens	16.5	9.8	0.247	0.809
Astragalus pelecinus (=Biserrula pelecinus)	1.0	0.5	0.013	0.051	Lavandula sp.	2.1	2.1	0.052	0.101
Atractylis cancellata	1.0	0.5	0.013	0.051	Leucas alba	2.1	6.4	0.162	0.101
Avena barbata	1.0	2.6	0.065	0.051	Leucas glabrata	6.2	5.9	0.149	0.303
Avena sp.	9.3	17.0	0.429	0.455	Lindenbergia indica	1.0	1.0	0.026	0.051
Barbeya oleoides	12.4	3.9	0.097	0.606	Lolium multiflorum	2.1	5.2	0.130	0.101
Barleria acanthoides	2.1	0.8	0.019	0.101	Lotus sp.	1.0	0.5	0.013	0.051
Barleria bispinosa	7.2	7.7	0.195	0.354	Lycium shawii	2.1	0.8	0.019	0.101
Barleria hochstetteri	1.0	0.8	0.019	0.051	Lysimachia arvensis subsp. arvensis (=Anagallis arvensis)	8.2	30.9	0.780	0.404
Barleria sp.	3.1	1.5	0.039	0.152	Maerua crassifolia	5.2	1.3	0.032	0.253
Bidens biternata	1.0	0.8	0.019	0.051	Malva parviflora	1.0	0.5	0.013	0.051
Blepharis edulis	19.6	53.9	1.358	0.960	Maytenus sp.	3.1	1.0	0.026	0.152
Boerhavia diffusa	2.1	0.8	0.019	0.101	Medicago minima	1.0	14.2	0.357	0.051
Boerhavia elegans	1.0	0.3	0.006	0.051	Medicago polymorpha	1.0	0.5	0.013	0.051
Boscia angustifolia (=Boscia integrifolia)	1.0	0.3	0.006	0.051	Medicago sp.	1.0	0.5	0.013	0.051
Brachiaria sp.	1.0	1.3	0.032	0.051	Melhania ovata	2.1	0.8	0.019	0.101
Brassica rapa	1.0	1.8	0.045	0.051	Melilotus indicus	1.0	6.4	0.162	0.051
Brassica sp.	1.0	0.8	0.019	0.051	Micromeria imbricata	21.6	36.1	0.910	1.061
Brassica tournefortii (=Coincya tournefortii)	4.1	27.6	0.695	0.202	Micromeria sp.	26.8	45.1	1.137	1.314
Bromus rigidus	1.0	3.1	0.078	0.051	Minuartia filifolia	8.2	4.6	0.117	0.404
Buddleja polystachya	3.1	0.8	0.019	0.152	Misopates orontium	1.0	0.5	0.013	0.051
Cadaba farinosa	3.1	1.3	0.032	0.152	Monolluma quadrangula (=Ceropegia quadrangula)	2.1	0.5	0.013	0.101
Cadaba glandulosa	3.1	1.0	0.026	0.152	Nepeta deflersiana	5.2	10.8	0.273	0.253
Calendula arvensis	1.0	6.4	0.162	0.051	Nicotiana glauca	14.4	10.8	0.273	0.707
Calotropis procera	11.3	5.4	0.136	0.556	Notoceras bicorne	1.0	9.0	0.227	0.051
Campanula edulis	1.0	0.5	0.013	0.051	Nuxia oppositifolia	5.2	3.9	0.097	0.253
Capparis cartilaginea	4.1	1.0	0.026	0.202	Ochradenus baccatus	1.0	0.3	0.006	0.051
Carduus pycnocephalus	1.0	0.5	0.013	0.051	Ocimum filamentosum	2.1	2.6	0.065	0.101
Carissa spinarum	9.3	7.2	0.182	0.455	Ocimum forskoelei	2.1	4.4	0.110	0.101
Caroxylon imbricatum (=Salsola imbricata)	2.1	4.6	0.117	0.101	Olea europaea	30.9	34.3	0.864	1.516
Caylusea hexagyna	1.0	0.8	0.019	0.051	Onopordum heteracanthum	3.1	1.3	0.032	0.152
Celtis africana	2.1	0.5	0.013	0.101	Opuntia ficus-indica	4.1	13.1	0.331	0.202
Cenchrus ciliaris	26.8	187.1	4.718	1.314	Orbea wissmannii (=Caralluma wissmannii)	2.1	1.0	0.026	0.101
Cenchrus setaceus (=Pennisetum setaceum)	28.9	47.7	1.202	1.415	Osteospermum vaillantii (=Tripteris vaillantii)	23.7	116.0	2.924	1.162
Cenchrus sp. (=Pennisetum sp.)	3.1	12.6	0.318	0.152	Osyris quadripartita (=Osyris lanceolata)	3.1	1.3	0.032	0.152
Centaurea pseudosinaica	2.1	2.1	0.052	0.101	Otostegia fruticosa	10.3	9.8	0.247	0.505
Centaurothamnus maximus	1.0	0.8	0.019	0.051	Oxalis corniculata	3.1	1.5	0.039	0.152
Cheilanthes pteridioides	3.1	9.5	0.240	0.152	Panicum turgidum	1.0	0.3	0.006	0.051
Chenopodium album	3.1	4.9	0.123	0.152	Paronychia sinaica	3.1	4.4	0.110	0.152
Chenopodium murale	1.0	0.3	0.006	0.051	Pentas lanceolata	2.1	1.5	0.039	0.101
Chrozophora oblongifolia	1.0	0.3	0.006	0.051	Pentatropis nivalis	3.1	11.0	0.278	0.152
Chrysopogon plumulosus	6.2	5.4	0.136	0.303	Periploca aphylla	19.6	11.1	0.279	0.960
Chrysopogon sp.	3.1	5.2	0.130	0.152	Periploca somaliensis	13.4	5.9	0.149	0.657
Cissus quadrangula	3.1	3.9	0.097	0.152	Phagnalon stenolepis	8.2	12.9	0.325	0.404
Cissus rotundifolia	13.4	20.6	0.520	0.657	Phoenix caespitosa	2.1	0.5	0.013	0.101
Citrullus colocynthis	1.0	1.3	0.032	0.051	Phragmanthera austroarabica	3.1	1.3	0.032	0.152
Clematis hirsuta	5.2	2.8	0.071	0.253	Phyllanthus sp.	1.0	0.5	0.013	0.051
Cleome gynandra (=Gynandropsis gynandra)	1.0	0.5	0.013	0.051	Picris scabra	4.1	5.7	0.143	0.202
Cleome scaposa	1.0	0.5	0.013	0.051	Pistacia falcata	12.4	3.9	0.097	0.606
Cleome sp.	3.1	1.0	0.026	0.152	Plantago afra	1.0	6.4	0.162	0.051
Clutia lanceolata	12.4	6.2	0.156	0.606	Plantago ovata	3.1	22.4	0.565	0.152
Coccinia grandis	8.2	9.5	0.240	0.404	Pluchea dioscoridis	1.0	2.8	0.071	0.051
Cocculus pendulus	1.0	0.3	0.006	0.051	Polycarpon tetraphyllum	1.0	0.5	0.013	0.051
Coleus arabicus (=Plectranthus asirensis)	3.1	6.2	0.156	0.152	Polygala abyssinica	11.3	6.4	0.162	0.556
Combretum molle	14.4	17.8	0.448	0.707	Portulaca oleracea	1.0	0.3	0.006	0.051
Cometes abyssinica	2.1	0.8	0.019	0.101	Portulaca quadrifida	1.0	0.8	0.019	0.051
Commelina forskaolii	4.1	2.8	0.071	0.202	Premna resinosa	4.1	4.6	0.117	0.202
Commelina sp.	2.1	1.0	0.026	0.101	Psiadia punctulata	26.8	64.7	1.631	1.314
Commicarpus grandiflorus	4.1	2.6	0.065	0.202	Psydrax schimperianus	3.1	2.6	0.065	0.152
Commicarpus plumbagineus	7.2	3.4	0.084	0.354	Pulicaria petiolaris	3.1	1.3	0.032	0.152
Commicarpus sp.	3.1	1.0	0.026	0.152	Pulicaria schimperi	5.2	2.1	0.052	0.253
Commiphora gileadensis	3.1	0.8	0.019	0.152	Pulicaria undulata	11.3	19.3	0.487	0.556
Commiphora kataf	3.1	1.8	0.045	0.152	Pupalia lappacea	18.6	26.0	0.656	0.910
Commiphora kua	1.0	0.5	0.013	0.051	Rhamnus staddo	2.1	0.5	0.013	0.101
Commiphora myrrha	12.4	6.2	0.156	0.606	Rhynchosia sp.	4.1	3.1	0.078	0.202
Conyza stricta	18.6	25.0	0.630	0.910	Ricinus communis	3.1	2.3	0.058	0.152
Coptosperma graveolens	4.1	2.1	0.052	0.202	Ruellia patula	2.1	1.5	0.039	0.101
Cordia monoica	2.1	0.5	0.013	0.101	Rumex nepalensis (=Rumex steudelianus)	1.0	0.8	0.019	0.051
Crassula schimperi	4.1	3.4	0.084	0.202	Rumex nervosus	11.3	7.0	0.175	0.556
Crepis sp.	3.1	12.1	0.305	0.152	Rumex vesicarius	10.3	17.3	0.435	0.505
Crinum album	3.1	1.0	0.026	0.152	Ruta chalepensis	3.1	1.0	0.026	0.152
Crotalaria sp.	17.5	18.8	0.474	0.859	Saccharum spontaneum	1.0	1.0	0.026	0.051
Cucumis sp	1.0	0.3	0.006	0.051	Sageretia thea	24.7	18.6	0.468	1.213
Cymbopogon sp.	1.0	0.8	0.019	0.051	Salsola tragus	9.3	11.3	0.286	0.455
Cynanchum viminale (=Sarcostemma viminale)	10.3	6.4	0.162	0.505	Salvadora persica	1.0	0.8	0.019	0.051
Cynodon dactylon	6.2	146.9	3.704	0.303	Salvia aegyptiaca	8.2	46.4	1.170	0.404
Cynoglossum bottae	2.1	1.8	0.045	0.101	Salvia dianthera (=Meriandra bengladensis)	1.0	1.3	0.032	0.051
Cynoglossum sp.	1.0	1.3	0.032	0.051	Salvia merjamie	1.0	0.3	0.006	0.051
Cyperus sp.	2.1	2.1	0.052	0.101	Sansevieria forskaliana (=Dracaena forskaliana)	1.0	1.5	0.039	0.051
Cyphostemma digitatum	7.2	11.1	0.279	0.354	Scandix pecten-veneris	1.0	2.6	0.065	0.051
Dactyloctenium aegyptium	1.0	1.3	0.032	0.051	Searsia glutinosa (=Rhus abyssinica)	2.1	0.8	0.019	0.101
Desmidorchis retrospiciens (=Caralluma retrospiciens)	9.3	3.6	0.091	0.455	Searsia natalensis (=Rhus natalensis)	1.0	0.5	0.013	0.051
Digitaria velutina	3.1	9.8	0.247	0.152	Searsia retinorrhoea (=Rhus retinorrhoea)	19.6	11.3	0.286	0.960
Dobera glabra	2.1	0.5	0.013	0.101	Seddera arabica	5.2	6.2	0.156	0.253
Dodonaea viscosa subsp. angustifolia	35.1	38.4	0.968	1.718	Seddera sp.	1.0	0.3	0.006	0.051
Dysphania ambrosioides (=Chenopodium ambrosioides)	1.0	1.0	0.026	0.051	Senegalia asak (=Acacia asak)	39.2	31.4	0.793	1.920
Dysphania schraderiana (=Chenopodium schraderianum)	13.4	41.0	1.033	0.657	Senegalia hamulosa (=Acacia hamulosa)	3.1	0.8	0.019	0.152
Ecbolium gymnostachyum	1.0	1.0	0.026	0.051	Senna alexandrina	1.0	0.3	0.006	0.051
Ecbolium viride	1.0	0.8	0.019	0.051	Silene sp.	5.2	3.1	0.078	0.253
Echinops sp..	12.4	10.6	0.266	0.606	Silene yemensis	2.1	11.9	0.299	0.101
Echium rauwolfii	2.1	26.3	0.663	0.101	Sisymbrium erysimoides	1.0	7.7	0.195	0.051
Ehretia obtusifolia	3.1	0.8	0.019	0.152	Sisymbrium irio	1.0	0.8	0.019	0.051
Ephedra foliata	4.1	1.0	0.026	0.202	Solanum incanum	32.0	23.2	0.585	1.567
Eragrostis papposa	29.9	172.9	4.361	1.466	Solanum schimperianum	9.3	4.4	0.110	0.455
Erica arborea	3.1	2.8	0.071	0.152	Solanum sp.	2.1	0.5	0.013	0.101
Erigeron bonariensis (=Conyza bonariensis)	1.0	0.3	0.006	0.051	Solanum villosum	6.2	4.6	0.117	0.303
Erodium cicutarium	6.2	9.3	0.234	0.303	Sonchus oleraceus	5.2	3.9	0.097	0.253
Erodium malacoides	5.2	10.8	0.273	0.253	Spergularia bocconei	1.0	1.3	0.032	0.051
Erodium moschatum	1.0	1.3	0.032	0.051	Stipagrostis ciliata	2.1	2.1	0.052	0.101
Erucastrum sp.	1.0	1.3	0.032	0.051	Stipagrostis obtusa	11.3	99.5	2.508	0.556
Euclea racemosa	2.1	2.1	0.052	0.101	Suaeda aegyptiaca	1.0	0.3	0.006	0.051
Euphorbia cuneata	1.0	0.3	0.006	0.051	Talinum portulacifolium	1.0	0.5	0.013	0.051
Euphorbia schimperiana	4.1	6.4	0.162	0.202	Tamarix nilotica	2.1	0.5	0.013	0.101
Euphorbia serpens	1.0	0.3	0.006	0.051	Tetrapogon tenellus	3.1	4.9	0.123	0.152
Euphorbia sp.	2.1	0.5	0.013	0.101	Tetrapogon villosus	4.1	5.4	0.136	0.202
Fagonia indica (=Zygophyllum indicum)	13.4	12.6	0.318	0.657	Teucrium sp.	1.0	0.5	0.013	0.051
Faidherbia albida	3.1	5.7	0.143	0.152	Teucrium yemense	13.4	15.5	0.390	0.657
Farsetia longisiliqua	6.2	4.1	0.104	0.303	Themeda triandra	26.8	191.5	4.828	1.314
Felicia abyssinica	8.2	18.8	0.474	0.404	Torilis arvensis	2.1	1.8	0.045	0.101
Felicia dentata	5.2	3.9	0.097	0.253	Torilis nodosa	1.0	0.5	0.013	0.051
Ficus cordata subsp. salicifolia	20.6	7.2	0.182	1.011	Tribulus parvispinus	1.0	1.8	0.045	0.051
Ficus ingens	15.5	5.4	0.136	0.758	Trichodesma sp.	4.1	1.0	0.026	0.202
Ficus palmata	7.2	2.3	0.058	0.354	Trifolium arvense	5.2	10.1	0.253	0.253
Ficus sycomorus	11.3	5.4	0.136	0.556	Trifolium campestre	3.1	9.0	0.227	0.152
Flueggea virosa	8.2	5.2	0.130	0.404	Triumfetta flavescens	11.3	9.8	0.247	0.556
Forsskaolea tenacissima	9.3	7.0	0.175	0.455	Triumfetta sp.	4.1	2.3	0.058	0.202
Fumaria abyssinica	3.1	1.8	0.045	0.152	Umbilicus horizontalis	2.1	2.6	0.065	0.101
Galium setaceum	1.0	0.5	0.013	0.051	Urospermum picroides	2.1	10.3	0.260	0.101
Galium sp.	2.1	1.0	0.026	0.101	Urtica urens	1.0	0.3	0.006	0.051
Geranium sp.	8.2	30.4	0.767	0.404	Vachellia etbaica (=Acacia etbaica)	5.2	2.3	0.058	0.253
Gladiolus dalenii	1.0	2.6	0.065	0.051	Vachellia flava (=Acacia ehrenbergiana)	18.6	22.2	0.559	0.910
Glinus lotoides	1.0	0.5	0.013	0.051	Vachellia gerrardii (=Acacia gerrardii)	5.2	3.9	0.097	0.253
Gomphocarpus fruticosus	11.3	6.7	0.169	0.556	Vachellia johnwoodii (=Acacia johnwoodii)	7.2	6.7	0.169	0.354
Grewia erythraea	5.2	1.3	0.032	0.253	Vachellia oerfota (=Acacia oerfota)	2.1	1.5	0.039	0.101
Grewia tembensis	9.3	6.2	0.156	0.455	Vachellia origena (=Acacia origena)	30.9	35.1	0.884	1.516
Grewia tenax	7.2	5.2	0.130	0.354	Vachellia tortilis (=Acacia tortilis)	9.3	7.0	0.175	0.455
Grewia trichocarpa	18.6	11.9	0.299	0.910	Vepris nobilis (=Teclea nobilis)	1.0	0.3	0.006	0.051
Grewia velutina	1.0	0.3	0.006	0.051	Verbascum sp.	9.3	7.5	0.188	0.455
Grewia villosa	5.2	2.6	0.065	0.253	Verbesina encelioides	3.1	3.1	0.078	0.152
Gymnosporia parviflora (=Maytenus parviflora)	41.2	47.7	1.202	2.021	Vermifrux abyssinica	1.0	0.8	0.019	0.051
Helichrysum glumaceum	9.3	10.8	0.273	0.455	Vernonia sp.	3.1	2.6	0.065	0.152
Helichrysum sp.	1.0	5.2	0.130	0.051	Veronica opaca	1.0	0.5	0.013	0.051
Heliotropium sp.	3.1	2.1	0.052	0.152	Vicia sativa	1.0	0.5	0.013	0.051
Hibiscus aponeurus	2.1	0.5	0.013	0.101	Withania somnifera	5.2	1.8	0.045	0.253
Hibiscus aponeurus	1.0	0.3	0.006	0.051	Xanthium spinosum	2.1	2.3	0.058	0.101
Hibiscus deflersii	9.3	7.7	0.195	0.455	Ziziphus spina-christi	11.3	4.4	0.110	0.556