Diversity and distribution of spontaneous plant communities and species in the northeast Algerian Sahara

Agrarian Academic Journal

agrariacad.com

doi: 10.32406/v7n3/2024/7-26/agrariacad

 

Diversity and distribution of spontaneous plant communities and species in the northeast Algerian Sahara. Diversidade e distribuição de comunidades e espécies de plantas espontâneas no nordeste do Sahara Argelino.

 

Mohamed Tahar Hanafi^1,2*, Djilani Ghemam Amara¹, Rabah Bounar³, Rabah Mayouf⁴, Ali Hachemi⁵, Abdelmoneim Tarek Ouamane²

 

^1*– Laboratory of Biology, Environment and Health, Department of Biology, Faculty of Life and Natural Sciences, Echahid Hamma Lakhdar University, El Oued, 39000, Algeria. Corresponding author. E-mail: hanafi-mohamedtaher@univ-eloued.dz

^2- Scientific and Technical Research Center on Arid Regions (CRSTRA), University Campus, Biskra, 07000, Algeria.

^3- Laboratory of Biodiversity and Biotechnological Techniques for the Valorization of Plant Resources (BTB-VRV), Department of Nature and Life Sciences, Faculty of Sciences, Mohamed Boudiaf University, M’sila, 28000, Algeria.

^4- Faculty of Life and Natural Sciences, Department of Agronomy, Echahid Hamma Lakhdar University, El Oued, 39000, Algeria.

^5- Ecology of Arid Ecosystems and Climate Risks Division, Scientific and Technical Research Center on Arid Regions (CRSTRA), University Campus, Biskra, 07000, Algeria.

 

Abstract

 

This study aims to comprehensively analyze plant diversity in the Northeast Algerian Sahara (El Oued region), quantitatively and qualitatively, focusing on species richness and diversity. The study sampled spontaneous vegetation from seven sites, analyzing the number of individuals, families, density, and richness. The results showed a ratio of generic richness to species richness of 0.94 ± 0.05, with a ratio of family richness to species richness of 0.56 ± 0.13. The dominant family was Chenopodiaceae, with 22.73%. The flora was dominated by perennial plants, with Sahara-Arabian elements being more abundant. Sufficient management strategies are required to protect biodiversity in these ecosystems.

Keywords: Species richness. Vegetation. Chenopodiaceae. Perennial plants. Algeria.

 

 

Resumo

 

Este estudo tem como objetivo analisar de forma abrangente a diversidade vegetal no Nordeste do Saara Argelino (região de El Oued), quantitativa e qualitativamente, com foco na riqueza e diversidade de espécies. O estudo amostrou vegetação espontânea de sete localidades, analisando número de indivíduos, famílias, densidade e riqueza. Os resultados mostraram uma relação entre riqueza genérica e riqueza de espécies de 0,94 ± 0,05, com uma relação entre riqueza familiar e riqueza de espécies de 0,56 ± 0,13. A família dominante foi Chenopodiaceae, com 22,73%. A flora era dominada por plantas perenes, sendo os elementos saara-árabes mais abundantes. São necessárias estratégias de gestão suficientes para proteger a biodiversidade nestes ecossistemas.

Palavras-chave: Riqueza de espécies. Vegetação. Chenopodiaceae. Plantas perenes. Argélia.

 

 

Introduction

 

The distribution and abundance of species are critical in ecology and biogeography (HUANG et al., 2016). The understanding of various taxa, their classification, characteristics, and preservation is an international scientific priority for biodiversity management and evaluation (COTTERILL, 1995). Wild plant diversity is an important component of our terrestrial habitats because it helps to maintain the region’s ecological stability and balance (ABDEL KHALIK et al., 2017). Despite being the world’s largest desert, the Sahara is also the most descriptive and representative because of its extreme aridity (BOUALLALA et al., 2022). Because of the high and the wide range of temperatures, the low and irregular precipitation, and long periods of droughts, the survival of many living creatures in this ecoregion is difficult (LE HOUÉROU, 1990; OZENDA, 2004) However, despite these challenging environmental conditions, several species have managed to persist and exhibit remarkable adaptations.

The varied and valuable Saharan spontaneous vegetation serves many purposes, most notably as grazing dromedary feed (BOUALLALA et al., 2013; CHEHMA and HUGUENIN, 2017), but it also plays a significant role in traditional medicine, which is widely used throughout the country (BENSIZERARA et al., 2013) to treat a variety of illnesses with a variety of plant bioactive substances (BRADAI et al., 2015).

Prior floristic surveys conducted on Sahara Desert habitats have employed a wide range of plant morphological descriptors, including chorological types for characterizing plant communities, Raunkiaer lifeforms, lifecycle/growth types, and so forth (QUÉZEL, 1965; BOUALLALA et al., 2013).

Camels raised for breeding graze the natural environments of the Algerian Sahara Desert, with varying degrees of preference depending on the habitat’s plant diversity, vegetation cover, and seasonal productivity (BOUALLALA et al., 2014). Even at this point, the majority of research on desert vegetation makes an effort to explain the diversity of plants that inhabit the investigated ecosystems by at least identifying the species that inhabit them. It is not always simple to implement such a straightforward technique, as desert-adapted animals adaptations change depending on how severe the local conditions are (BRADAI et al., 2015).

Despite many studies focused on protecting Algerian vegetation and Saharan flora (ABDELKRIM et al., 2015), research on plant communities in specific habitats (arid, semi-arid, and desert regions) remains limited. These hot and dry environments are thought to be particularly fragile ecosystems due to the disturbance by desertification and overgrazing (BOUZEKRI et al., 2023), This disturbance could reduce habitat productivity and ecosystem stability (BOUALLALA et al., 2022). Hereafter, the use of functional plant traits provides a reliable method for understanding interactions between vegetation and the environment (CHENCHOUNI, 2017; KOUBA et al., 2021).

The objective of this research is to evaluate the diversity of plants in the Northeast Algerian Sahara (El Oued region) through both quantitative and qualitative techniques. Our primary focus is to analyze the plant community by examining plant traits, as they provide valuable insights into the connection between vegetation and its environmental distribution. Furthermore, this assessment will help determine the state of biodiversity in the desert lands.

 

Materials and methods

 

1. Study area and data collection

 

The area of ​​study is situated in the Algerian Sahara’s northeast (34°6’40″N, 6°13’44.51″E), in the region of EL Oued (Figure 1). The climate of the study area is arid to hyperarid ‘desertic’ during the period (1987- 2022). Climatic data were obtained from the weather stations of Biskra and EL Oued (Guemar).

 

Figure 1 – Geolocalization map showing the location of sampling sites in the Northeast part of the Algerian Sahara (EL Oued).

 

The data confirmed that climate condition is characterized by dry season throughout the whole year, with an average temperature ranging from 12.03 °C to 34.62 °C for January and July months, respectively in the region of Biskra and 10.97 °C to 33.98 °C for January and July months, in the region of El Oued.

The average annual rainfall was marked by low amounts of 144.30 mm in Biskra and 79 mm in El Oued and extremely irregular (41.20 mm in 2022 to 343 mm in 1994), (16.24 mm in 1989 to 350 mm in 2004) Specifically in Biskra and El Oued, the lowest value is recorded in August with 2.84 mm (Biskra) and 0.52 mm in July (El Oued), and the highest value in September at 22.85 mm (Biskra) and in November at 20.27 mm (El Oued) (Figure 2).

 

Figure 2 – The ombrothermic diagram of Gaussen and Bagnouls of (a) Biskra and (b) ELOued in the Northeast part of the Algerian Sahara. The mean precipitation in (mm) and temperature in (°C) are monthly averages on long-term climatic data from 1987 to 2022; the diagram confirms a dry period that lasts all year.

 

2. Selection of the sampling sites

 

Before the selection of sampling sites, the study region was visited throughout the year many times to investigate the diversity of spontaneous plant communities. Seven (7) sites were selected based on the geomorphology of the landscape, altitude and homogeneity of the ecological conditions (Figure 1).

Site 1 (The altitude = 27 m above the sea level) indicates a micro dune where dominates Anabasis articulata, site 2 (The altitude = 21 m above the sea level) indicates a micro dune with A. articulata, Salsola tetragona and Zygophyllum album as distinctive vegetation species, site 3 (The altitude = 8 m below the sea level) is a Wadi bed with sand, where dominates A. articulata and Traganum nudatum, site 4 ( The altitude = 22 m below the sea level) is salty soil where dominates A. articulata, S. tetragona and T.nudatum, site 5 (The altitude = 18 m below the sea level) is a sandy soils that has A.articulata and T. nudatum, characteristics, site 6 ( The altitude = 16 m below the sea level) is a sand dunes where dominates T. nudatum, L. guyonianum and site 7 (The altitude = 2 m above the sea level) is a sand dunes where A. articulata and Retama retam are abundant.

Given the pedoclimatic context, the soil’s physical and chemical characteristics of the sampling sites show a high salinity, especially for site 2 and site 4 (electrical conductivity (1/5) = 2.6 dS/m). They often have a sandy texture and an alkaline pH (pH = 7.44–8.08) with a very low organic matter content (less than 2%), and little to moderately calcareous (CaCO₃ the range of content 1, 44 to 12%) (LOZET and MATHIEU, 1990).

 

3. Plants sampling and data collection

 

The data collection was carried out from May 2022 to the end of April 2023, which corresponds to the period of full plant growth and to find the maximum number of spontaneous plants to this dry period that affects the study area. We selected seven (7) sampling sites to carry out our measurements. We ensured that the sample sites had almost the same environmental conditions. A line transect method was used to assess the vegetation, five (05) transects (North South) in each of the seven sites were sampled. In, total we have 35 transects in the whole study area. For estimating plant abundance and richness, we utilized the Point-Intercept Method. For each transect, we identified the species of plants every 20 cm. In every transect, every species’ density was determined. The recognition of plant species was achieved by consulting Algerian flora identification books (QUÉZEL and SANTA, 1963; OZENDA, 2004).

 

4. Plant diversity Analysis

 

4.1. Diversity indices

 

Several alpha-diversity descriptors (species richness, Shannon diversity index, and evenness), as well as beta-diversity descriptors (Jaccard index and Bray-Curtis distance), were used to evaluate the floristics’ richness and diversity at every single sample site. When computing alpha diversity, the data gathered from sample plots were handled separately; however, when calculating beta-diversity indices utilizing summing of the species’ abundances from sample plots, the data from the sample plots were combined. Moreover, the species richness measured at the sample locations was compared using a scale for species richness used in Saharan environments (DAGET and POISSONET, 1991). As a result, the condition of the flora was established for each location based on the number of species (S) as: Very low species richness (S < 11), low species richness (S = 11–20), moderate species richness (S = 21–30), fairy species richness (S = 31–40), species richness (S = 41–50), and very high species richness (S > 50) flora (AZIZI et al., 2021). Shannon diversity index (H’) used for measuring the diversity of plant alpha. The Shannon diversity index (H’) is influenced by the diversity of common species (SHANNON and WEAVER, 1949).

(1)

The species richness (S) denotes the total number of species present in the sampling site (MAGURRAN, 2021), N is the total number of individuals of S species, and ni is the number of individuals of species i in the sampled site. The Shannon diversity index to theoretical maximum diversity ratio was used to calculate the evenness index “E”.

	(2)
	(3)

The distribution of individuals within a species may be measured using evenness (E). It has a value between 0 and 1. Maximal evenness (E = 1) is defined when all plant species have densities that are quite close to one another. The assessment of evenness is helpful for identifying a community’s structure since it works well to identify anthropogenic alterations (NEFFAR et al., 2018). The taxonomic structures for each sample location were used to analyse the phylogenetic diversity using ratios of the generic or the family richness to species richness (G/S or F/S). As a result of habitat and environmental circumstances, communities’ taxonomic structures differ. We predicted that the hierarchical taxonomic categories richness (family, genus and species) could rise in accordance with the more favourable ecological conditions in sampling areas. Power models that were linearized following natural logarithm (ln) transformations were used to study the correlations between the richness of species and the richness of the generic or the family (FAN et al., 2017). In previous research to mimic both sorts of relationship the following models have been successfully used.

	(4)
	(5)

Regarding the species ‘genus and family’ relationships, where the numbers (G), (F), and (S) represent the number of genera, families, and species, respectively. The variance of (G/S) and (F/S) ratios among sample locations was examined using a one-way ANOVA.

 

4.2. Beta diversity

 

The Jaccard index, which uses data on species presence/absence per site, was used to examine the qualitative spatial similarity “beta diversity” of plant variety between sample sites, and the Bray-Curtis distance, which uses data on average species densities per site, was used to assess the quantitative spatial similarity (beta diversity). To separate homogenous groups of sample sites based on their species composition and abundance, a clustering analysis (Ward’s approach) was performed to the similarity analysis findings. R software was used to carry out all of the statistical analyses discussed above (R CORE TEAM, 2022).

 

4.3. Morphological types

 

According to Quézel and Santa (1963) and Ozenda (2004) the classification of a plant as perennial or annual depends on how long the aerial vegetative portion persists throughout the unfavourable season (BOUALLALA et al., 2020).

 

4.4. Plant life form

 

According to Raunkiaer (1934), plants may be classified based on their biological form, or “life form,” which is dictated by the species’ morphology and represents the expression of its adaptability to its environment, which is connected to the preservation of the meristem. Considered four types of life: Chamaephytes, Phanerophytes, Hemicryptophytes and Therophytes.

 

4.5. Phytogeographical types

 

The flora of Algeria and desert regions (QUÉZEL and SANTA, 1963; QUÉZEL, 1978) was used to establish the phytogeographical properties of the surveyed plant species; numerous chorological groupings were created from the division of phytogeographical systems: endemic to the Sahara, Saharo-Arabian, Mediterranean, Cosmopolitan, etc.

 

Results

 

1. Floristic composition

Throughout the research period, a total of 3885 individuals belonging to 44 species can be grouped into 36 genera and 16 families. The Chenopodiaceae family hold 22.73% of the total of species; Fabaceae follows it with 18.18%, Asteraceae with 11.36%, Brassicaceae, Caryophyllaceae and Zygophyllaceae with 6.82% each, and Cucurbitaceae and Poaceae with 4.55% of species. The remaining 8 families represent only 18.18% of the total species (Table 1). Moreover, it was identified with a maximum density in site 3 (670 individuals/50 m) followed by site 4 (618 individuals/ 50 m) and the minimum in site 7 (388 individuals/50 m). Amongst the observed species, Anabasis articulata and Traganum nudatum represented the most uppermost densities with a totality of 859 and 514 individuals/50 m, respectively. Anabasis articulata was dominant in sites 1, 3, 4 and 7 with mean densities of 22.00 ± 1.58 to 41.40 ± 2.07 individuals/relevé; site 6 recorded the minimum with (12.80 ± 1.92 individuals/relevé). Traganum nudatum dominated at site 6 with 18.40 ± 2.79 individuals/ relevé.

 

2. Taxonomic structures

 

In general, the ratio of (G/S) generic richness to species richness in the Northeast part of the Algerian Sahara (EL Oued) was 0.94 ± 0.05, while the ratio of (F/S) family richness to species richness was 0.56 ± 0.13 (Figure 3). Values of the ratios of (G/S) were high in all sampling sites; site 4 saw a total of 1.00, while the minimum value was observed in site 4 (F/S = 0.39 ± 0.05).

 

Figure 3 – Family richness ratios to species richness (F/S) and generic richness to species richness (G/S) for different study sites in the Northeast part of the Algerian Sahara (EL Oued).Following the Tukey’s HSD post hoc test, The identical letters related to the means of the ratios of F/S (lower-case letters) and G/S (upper-case letters) are not substantially unalike (P>0.05) between sample sites. Standard deviations are represented by the vertical error bars.

 

Table 1 – Taxonomic diversity and plant density list at several different sites in the Northeast part of the Algerian Sahara (EL Oued). Plant density is presented as the mean (± standard deviation) of the number of individuals (per 50 m) counted in five transects inside each site; while plant density expressed as total species abundances across all sample sites are listed in the ‘Total’ column. The relative frequency of the species richness that makes up each family is shown by percentages connected with family names.

Family	Species	Sampling sites
		Site 1	Site2	Site 3	Site 4	Site 5	Site 6	Site 7	Total
Apiaceae (2.27%)	Ferula vesceritensis Coss. & Dur.	―	0.80 ± 1.79	―	―	―	―	―	4
Asclepiadaceae (2.27%)	Pergularia tomentosa L.	5.00 ± 1.41	1.20 ± 2.68	―	―	―	―	―	31
Asteraceae (11.36%)	Atractylis flava L.	―	8.60 ± 7.98	2.40 ± 0.55	―	―	―	―	55
	Atractylis serratuloides Sieber.	16.00 ± 8.6	0.40 ± 0.89	4.40 ± 1.52	―	―	2.20 ± 1.09	2.60 ± 0.55	128
	Cotula cinerae Del.	―	0.80 ± 1.09	―	―	―	―	―	4
	Launaea resedifolia O.K.	3.00 ± 1.41	―	―	―	―	―	―	15
	Rhantherium suaveolens Desf.	4.40 ± 3.21	―	―	―	―	―	―	22
Boraginaceae (2.27%)	Heliotropium bacciferum Forsk.	1.80 ± 1.79	―	―	―	―	―	―	9
Brassicaceae (6.82%)	Diplotaxis harra (Forssk.) Boiss.	2.40 ± 3.05	1.20 ± 2.68	―	2.20 ± 2.68	―	―	―	29
	Malcolmia aegyptiacaSpr.	0.20 ± 0.45	―	―	―	―	―	―	1
	Matthiola livida (Del.) DC.	0.40 ± 0.89	―	―	―	―	―	―	2
Caryophyllaceae (6.82%)	Gymnocarpos decander Forsk.	8.80 ± 3.27	―	―	―	―	1.40 ± 1.67	―	51
	Herniaria fontanesii J. Gay	1.00 ± 1.41	0.40 ± 0.89	―	―	―	―	―	7
	Polycarpaea repens (Forsk.) Asch. et Schw.	6.20 ± 2.17	―	―	―	―	―	―	31
Chenopodiaceae (22.73%)	Anabasis articulata (Forsk) Moq.	26.00 ± 2.74	13.00 ± 3.54	31.80 ± 2.28	41.40 ± 2.07	24.80 ± 1.92	12.80 ± 1.92	22.00 ± 1.58	859
	Atriplex halimus L.	―	8.80 ± 5.31	4.00 ± 2.55	―	―	―	―	64
	Cornulaca monacantha Del.	―	4.80 ± 3.42	2.20 ± 0.45	―	4.80 ± 2.28	5.00 ± 1.00	3.00 ± 0.71	99
	Haloxylon articulatumBoiss.	―	―	9.80 ± 2.77	―	―	―	―	49
	Salsola foetida Del.	―	―	3.20 ± 1.92	―	―	―	―	16
	Salsola tetragona Del.	―	13.00 ± 9.41	―	25.00 ± 3.94	17.60 ± 3.05	―	―	278
	Salsola vermiculata L.	―	5.80 ± 7.82	―	―	―	―	―	29
	Suaeda mollis (Desf.) Del.	―	11.00 ± 10.00	1.40 ± 1.34	―	0.40 ± 0.89	―	―	64
	Suaeda fruticosa L.	―	1.60 ± 3.58	―	10.00 ± 3.08	2.40 ± 2.30	―	―	70
	Traganum nudatum Del.	1.80 ± 2.68	10.00 ± 9.56	22.40 ± 3.05	21.80 ± 1.30	21.60 ± 1.14	18.40 ± 2.79	6.80 ± 1.30	514
Cistaceae (2.27%)	Helianthemum lippii (L.) Pers.	2.60 ± 2.79	0.40 ± 0.89	―	―	―	―	―	15
Cucurbitaceae (4.55%)	Citrullus colocynthis Schrad.	2.60 ± 2.61	0.60 ± 1.34	―	―	―	―	―	16
	Ecballium elaterium Rich.	―	―	0.40 ± 0.89	―	―	―	―	2
Ephedraceae (2.27%)	Ephedra alata DC.	―	―	7.00 ± 1.58	―	―	7.20 ± 1.64	7.40 ± 1.34	108
Fabaceae (18.18%)	Astragalus crenatus Schult.	1.60 ± 2.30	―	―	―	―	―	―	8
	Astragalus mareoticus Del.	0.40 ± 0.89	―	―	―	―	―	―	2
	Argyrolobium uniflorum (Decne.) Jaub&Spach.	―	1.20 ± 2.68	―	―	―	―	―	6
	Astragalus armatus Willd.	1.00 ± 1.41	1.60 ± 3.58	―	―	―	―	―	13
	Astragalus gombiformis Pomel.	―	―	2.20 ± 1.48	―	―	―	―	11
	Genista saharae Coss.& Dur.	2.40 ± 1.67	―	―	―	―	―	―	12
	Lotus halophylus Boiss. et Spr.	0.60 ± 1.34	―	―	―	―	―	―	3
	Retama retam Webb.	―	0.80 ± 1.79	13.60 ± 3.51	―	7.80 ± 2.68	11.20 ± 0.84	10.60 ± 1.14	220
Plombaginaceae(2.27%)	Limoniastrum guyonianum Boiss.	―	6.20 ± 7.89	12.60 ± 1.67	―	14.00 ± 1.87	16.80 ± 2.49	10.20 ± 1.79	299
Poaceae (4.55%)	Aristida acutiflora Trin. et Rupr.	―	6.00 ± 5.87	―	―	―	8.40 ± 2.30	2.80 ± 0.84	86
	Aristida pungens Desf.	10.6 ± 3.78	6.00 ± 8.25	―	―	―	9.00 ± 1.87	7.20 ± 1.64	164
Rutaceae (2.27%)	Haplophyllum tuberculatum (Forsk.) Juss	2.40 ± 2.51	―	―	―	―	―	―	12
Tamaricaceae (2.27%)	Tamarix gallica L.	―	―	3.80 ± 2.28	―	―	―	―	19
Zygophyllaceae (6.82%)	Fagonia glutinosa Del.	―	2.20 ± 2.05	―	―	―	―	―	11
	Zygophyllum album L.	―	11.60 ± 2.51	12.80 ± 3.35	14.60 ± 3.36	18.80 ± 2.95	10.60 ± 1.82	5.00 ± 1.00	367
	Peganum harmala L.	0.80 ± 1.30	1.20 ± 1.64	―	8.60 ± 3.21	5.40 ± 3.97	―	―	80
Total		510	596	670	618	588	515	388	3885

 

In accordance with one-way ANOVA, between the sample sites, there were substantial differences in both ratios’ values, where the F/S ratio (F_{(6, 34)} = 41.88, P < 0.001) demonstrated a substantially larger variability compared to the G/S ratio (F_{(6, 34)} = 6.98, P < 0.001).The correlations between species richness and richness of higher taxa (i.e., genus and family) are assessed using linearized power functions, which are presented in Figure 4. The power model’s exponents of (a) “ln (F or G) = a x ln (S)” showed variance in both family-species and genus-species connections. Based on the R² values for the models’ goodness-of-fit ratings, In contrast to the family-species relationship, the linearized model of the relationships between genera and species showed a high level of stability. Relationships between families of species and genera of species were both favourable and statistically significant in all sample sites (linear regressions: P < 0.01).

 

Figure 4 – Relationships between species richness (S) and family (F)/ generic (G) richness at different sampling sites in the Northeast part of the Algerian Sahara (El Oued). Points’ colours correspond to the sites of sampling, and the taxonomic ratios are represented with size values are set to (a) F/S and (b) G/S. Simple linear regression is shown by the solid blue lines, which have light grey 95% confidence zones. A measure of the linear regression model’s goodness-of-fit is the R-squared.

 

3. Plant diversity

 

The richness of species in sample sites varied between 7 and 26 species; Depending on the landscape, it varied. Generally speaking, there was relatively low floristic diversity. Species richness varied between poor in sites 3 and 6 (S = 16 species, S = 11 species) respectively, or very poor (< 11 species) in the sites 4, 5 and 7 where species richness ranged between 7 and 10, but in sites 1 and 2 the species richness is moderate (Table 2). According to the measurement of biodiversity that demonstrated that site 2 had the uppermost value in Shannon Index (H = 2.81) and site 4 had the bottommost values (H = 1.70). In the Sites 1,3 and 5,7 Shannon index values were in a variety of 2.02 and 2.51. Sites 6 and 7 had the most equilibrium-matched plant communities (E = 0.80 to 0.84), after that sites 4 and 5 (E = 0.75–0.78). Site 1 was recorded as the lowest evenness of value (E = 0.53). Site 2 exhibited the greatest values of species richness and Shannon index, although also displayed relatively low evenness due to the existence of several rare species.

 

Table 2 – The plant communities’ diversity parameters of different sites in the Northeast part of the Algerian Sahara (El Oued).

	Sampling sites
Diversity parameters		Site 1	Site 2	Site 3	Site 4	Site 5	Site 6	Site 7
Species richness		23***	26***	16**	7*	10*	11**	10*
Shannon index		2.51	2.81	2.34	1.70	2.02	2.22	2.09
Maximum Shannon index		2,60	2,86	2.40	1.75	2.06	2.27	2.15
Evenness index		0.53	0.63	0.65	0.78	0.75	0.84	0.80

*: very species-poor flora, **: species-poor flora, ***: species moderate flora.

 

4. Plant diversity Similarity analysis between phytoecological sites

 

The species distribution between the sampling sites in represented by the diagram of Venn in Figure 5. According to the diagram, there are two species (Anabasis articulate and Traganum nudatum) distributed and common to all of the study sites. Site 1 had the majority of the species that were shared. Site 1 had eleven different species exclusively, and Site 2 and Site 3 each had five species, however, Sites 4 –7 did not have any unique species, meaning that all of their species were also found at other locations (Figure 5). For site 1, these species were Launaea resedifolia, Rhantherium suaveolens, Heliotropium bacciferum, Malcolmia aegyptiaca, Matthiola livida, Polycarpaea repens, Astragalus crenatus, Astragalus mareoticus, Genista saharae, Lotus halophylus, and Haplophyllum tuberculatum; Ferula vesceritensis, Cotula cinerae, Salsola vermiculata, Argyrolobium uniflorum, and Fagonia glutinosa for site 2; haloxylon articulatum, Salsola foetida, Ecballium elaterium, Astragalus gombiformis, and Tamarix gallica for site 3 (Table 1).

 

Figure 5 – The Seven-set Venn diagram is demonstrating plant’s species richness (S) collected at different sites in the Northeast part of the Algerian Sahara (El Oued). The species’ number in every sample site is shown by the value of S stated in square brackets, whereas the diagram’s numbers represent species that are solely present exclusively between the related sites.

 

The plant community similarity qualitative analysis among sites using Jaccard index has shown the uppermost resemblance results between sites 6 & 7 (resemblance = 60.10%) and sites 4 & 5 (resemblance = 55.80%). These four sites as well as the sites 2 & 3 have been set as a homogenous cluster which possessed high similarities of the composition of the plant (Figure 6). For the calculable quantitative similarity that was measured using Bray-Curtis distance based on the abundant data of the plant, sites 6 & 7 (similarity = 99.80%), sites 4-5 (similarity = 91.30%) and sites 3- 7 (similarity = 85.20%) had shown the uppermost similarity values. The gathering analysis had demonstrated that sites 4, 5, 6 and 7 had quantitatively alike plant structure, while sites 3, 6, 7 and 2,4 and 5 were homogenous as well. Intergroup similarities among sites that consist the two groups were low.

 

Figure 6 – Heatmaps and dendrograms (side colored plots) of the hierarchical clustering analysis (Ward’s method), representing the similarity matrix of plants between sampling sites of the Northeast part of the Algerian Sahara (EL Oued). According to similarity scores, the intensity of the colour reflected the similarity: (a) coefficient of Jaccard and (b) Bray and Curtis distance. On the basis of plant composition, homogenous groups of sites are represented by yellow rectangles inside the heatmap matrix.

 

5. Plant functional traits

 

5.1. Life forms

 

According to Figure 7, the chamaephytic species (62.14%) which included species 9,15,12,5,8 and 7 had the uppermost values in the biological spectrum of life forms across all the sites. There are just 5 chamaephyte species and 2 therophyte species at Site 4. Hemicryptophytes species (13.59%) are found throughout the biological spectrum of life forms, with the exception of sites 4 and 5, at sites 1, 2, 3, 6, and 7, where there are 4, 5, 1, 2, and 2 species, respectively. Only sites 1, 2, 3, 4, and 5 had therophytes (17.48%), which included 9, 5, 1, 2, and 1 species. Except for site 4, all of the sites’ phanerophytes (6.80%) were represented by three species: Retama retam in sites 2,3,5,6 and 7, Tamarix gallica in site 3, and Genista saharae in site 1.

 

5.2. Morphological types

 

The flora consisted of 5 annuals (6.80%) and 39 perennial plants (93.20%), as far as morphological characteristics were concerned. Only sites 1, 2, and 4 have annual species, while all of the sites have perennial species, with site 2 having the highest number (25 species), and perennial species being widely distributed (Figure 7).

 

5.3. Chorological types

 

The Saharo-Arabian category was highly represented throughout the whole research region based on chorological types, with the highest level in the site 2 (14 species) and the site 1 (12 species) (Figure 7). The Mediterranean chorological element was seen in all of the sites, with four species at the greatest level and one species at the lowest level in sites 4–7. We identified the Saharan endemic element and Mediterranean element at all sites.

 

Figure 7 – (a) Life forms, (b) morphological types and (c) chorological types Distribution for different sampling sites of the Northeast part of the Algerian Sahara (El Oued); Histograms contain numbers that represent the number of plant species.

 

Discussion

 

The current study focused, for the first time, on a thorough examination of the diversity of plant communities occurring in the northeastern Algerian Sahara (El Oued). Identifying plant species diversity and the biological characteristics of vegetative communities in natural habitats is critical for ensuring the survival and preservation of species, communities, habitats, and ecosystems (GAMOUN, 2013).

The flora of the study area included 44 species from 16 families and 36 genera. The most widespread families were Chenopodiaceae (10 species), Fabaceae (8 species), and Asteraceae (5 species), representing 22.73%, 18.18%, and 11.36%, respectively. These botanical families predominate in Saharan environments, consistent with findings from Tunisia (GAMOUN et al., 2018), Algeria (CHENCHOUNI, 2012; MACHEROUM et al., 2021), and the Egyptian Saharan Oasis (SALAMA et al., 2018).

According to plant abundance data, perennial species are the predominant functional group in the study region. Chehma and Huguenin (2017) indicated that perennial vegetation is essential for providing nourishment to camels in an extensive grazing setup. In terms of plant density, Anabasis articulate and Traganum nudatum are the most abundant, accounting for 22% and 13% of the total, respectively. Different habitats and adaptation characteristics can explain variations in species density, frequency, and abundance (ZHANG et al., 2021; ULLAH et al., 2022).

The study revealed that 50% of the 16 botanical families examined contained only one species. This is a common trait of desert plants that suggests their ability to adapt and survive in dry conditions (AZIZI et al., 2021; BOUALLALA et al., 2023). Only a few species from larger plant families can adapt and survive, while others become extinct. Previous studies conducted by Abd El-Khalik et al. (2017), El-Sheikh (2021), and Meddour et al. (2023) have demonstrated that areas with a wider range of species have more species distributed across multiple genera, compared to areas where most species belong to the same genus. The high values of the coefficient reflect the primary characteristics of desert flora, which has a low diversity. Accordingly, this indicates that the species has adapted well to xeric conditions (CHENCHOUNI, 2012; ABDEL KHALIK et al., 2017). In arid areas, most plant families are represented by only one or two genera and most genera by one or two species (KOUBA et al., 2021).

Correlation tests showed that differences in taxonomic structure can vary significantly between plant communities based on environmental conditions (FAN et al., 2017). This is consistent with our findings, where the G/S ratio exceeded 89% and the F/S ratio exceeded 43%. These results are consistent with those reported by Oitsius et al. (2021) in Ukraine. Species richness is low in all sampling sites, reflecting the low plant diversity of these environments. These findings are consistent with previous studies that examined the vegetation of rangelands in the country’s north. Bouallala (2013) found moderate floristic diversity in arid rangelands of the Algerian Sahara Desert. Despite that desert covers more than 84% of its land, Algeria stands out among the Mediterranean countries in terms of taxonomic diversity. According to Quézel (1995), it is the region’s seventh most abundant plant species. According to Abdelaal et al. (2018), it is the second most common native plant in North Africa, with 3951 taxa. Algeria also has 248 endemic plant taxa, representing 6.3% of its total flora. This level of strict endemism is slightly higher than those found in other arid North African countries such as Libya (6%), Tunisia (2.6%), and Egypt (2.3%).

The dominance of chamaephytes in the study area appears to be due to the adaptations to a hot, dry environment, topographic differences, animal and human impacts (EL-DEMERDASH et al. 1995). Furthermore, they exert strong stomatal control (BRADAI et al., 2015). Therophytes have low species diversity across the research area, with nine species present at site 1, 5 and at site 2. According to Abdel Khalik et al. (2017), the lack of precipitation in the Saharan climate is most likely responsible for the poor representation of therophytes, which are in seed form during their vegetative period. Moreover, the soil is characterized by low water retention capacity (BARKOUDAH and VAN DER SAR, 1982; MONOD, 1992). The presence of therophytes in sites 1 and 2 can be attributed to their role as a transitional zone between the north and south regions of the country. The semiarid-arid climates found in these sites create a separation between the humid and subhumid environments of the north and the arid and hyper-arid climates of the south (ALLIOUCHE and KOUBA, 2023). Hemicryptophytes are present in all sites except those that lack sand completely. According to Bouallala (2013), psammophytes are the most common vegetation type of hemicryptophytes found in sandy soils and dunes. The phanerophytes recorded in the study area include three species: Genista saharae, Retama retam, and Tamarix gallica. It is uncommon to find phanerophytes in arid environments, except wadis and valleys, which are their most suitable habitats (BRADAI et al., 2015).

The analysis of floristic data revealed that Saharo-arabian elements are more abundant than other floristic elements in the research area. This can be attributed to the study’s location in the Algerian Sahara, which is part of the Saharo-arabian phytogeographical region (AZIZI et al., 2021; BOUALLALA et al., 2023). Furthermore, analyzing plant species’ life forms can reveal important information about how vegetation responds to environmental changes (HUSEYNOVA, 2022; ULLAH et al., 2022). In this study, chamaephytes were found to be the dominant life form. Chamaephytes’ widespread presence can be attributed to their ability to withstand drought and salinity (BOUALLALA et al., 2023). The preservation of threatened flora necessitates the implementation of specific management measures that ensure their long-term survival.

 

Conclusions

 

This study sheds light on the floristic composition, lifeforms, morphological types, chorological categories, and community structure of spontaneous vegetation in the northeastern Algerian Sahara. The species richness in these habitats reached 44 species, generally represented by perennial plants. Among the 16 families listed, Chenopodiaceae, Fabaceae, and Asteraceae were the strongest. Based on climatic parameters and geomorphological characteristics, the northeastern part of the Algerian Sahara represents hyper-arid environments with low plant diversity and vegetation cover. This perennial vegetation provides a variety of benefits that can meet the needs of the local population. It serves as a source of traditional medicine and provides forage for dromedaries throughout the year. This study highlights the significance of plant traits in understanding the organization of plant communities in harsh desert environments like the Northeast Algerian Sahara. The vegetation of the study area is dominated by chamaephytes and therophytes, indicating their vulnerability to arid conditions and unique evolutionary techniques. Therophytes are less common because they are the primary source of free grazing during the period immediately following rainy events. The Saharo-arabian chorological (phytogeographic) element is a good indicator of the Saharan climate. However, the presence of the Saharan endemic element reflects the uniqueness of certain plants that inhabit and prefer the Saharan environment.

 

Acknowledgments

 

The research was supported by the Ministry of Higher Education and Scientific Research of Algeria, and the Department of Biology, Faculty of Life and Natural Sciences, University, El Oued.

 

Conflicts of interest

 

The authors declare no conflict of interest.

 

Authors’ contribution

 

All authors contributed equally for this work.

 

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Received on February 24, 2024

Returned for adjustments on July 22, 2024

Received with adjustments on July 23, 2024

Accepted on July 26, 2024

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