The current state of the plant diversity in the Tlemcen region ( Northwest Algeria )

Tlemcen region is characterized by a Mediterranean climate, with a remarkable vegetal cover. The latter is influenced by the anthropozoological action. For that, we realized a phytoecological study based on the minimum area classical method [1] which allows us to have a good overview on plant biodiversity and better analyze and interpret the vegetation at different levels (systematic composition; biological, morphological and biogeographical characterizations; stratification; and plant species inventory which we hope comprehensive). The results show that our ecosystems are disrupted because therophytisation, before last vegetation dynamics element [2], settles giving up a few feet of cork and holm oaks species of ancient forest.


INTRODUCTION
The nature and actual composition of Mediterranean plant communities cannot be understood without taking into account geological, paleoclimatic and anthropogenic factors that marked the evolution of various ecosystems specific to that biogeographical zone.
The current Mediterranean region can be defined by evident floristic criteria since 50%, of some 25,000 species in the Mediterranean climatic area [3,4] and more so in the Mediterranean bioclimatic zone [5], are endemic [6].
Biodiversity includes three levels of biological variability: ecosystem complexity, species richness and genetic variation [7].
Mediterranean plant biodiversity is the product, for many, of a traditional and harmonious environment use by man [8].Despite the constant attacks they have suffered, for over a millennium, Mediterranean forests still offer, in some locations, a significant development.
The problem posed by the dynamics of non-tree structures (steppe, shrubland and lawns) can however lead to the understanding that their current expansion has been and is still under the human action impact, mainly through fire and grazing, but also the clearing [9].
In most North Mediterranean countries (France, Spain, etc.) these attacks are somehow controlled and give a biological rise, while in the Southern Mediterranean countries (Algeria, Morocco, Tunisia, etc.) they continue in an uncontrolled manner.[10] emphasizes that "the analysis of the floristic richness of different groups and their biological and chronological characteristics allows to demonstrate their floral originality, conservation condition and, consquently, their heritage".
The flora of Algeria is characterized by a remarkable level of endemism (12.6% or 653 species listed on the 3139 including 7 endemic tree species [11].
However, Tlemcen region is not immune to Circum-Mediterranean natural laws.It has a very diverse flora and closely linked to various stressors.This vegetation has been largely studied; we can quote [12][13][14][15][16].

LOCATION
The study is located in the north-western part of Algeria.The study area is divided into two parts: one located in the mountains of Tlemcen and the other near the coast with rugged mountainous terrain (integral part of Traras Mountains).The stations choice mainly depends on the presence of pre-forest formations and shrubland.The area studied is located between 34˚ and 35˚25' North and 0˚55' and 2˚30' west and covers a 9017.69km² area.It is limited geographically (Figure 1 The stations were chosen based on the vegetation homogeneity.

Biological Material
(See the biological spectrum): biological material.

Method
Four areas and three strata were defined in the ecological zoning.Areas are represented by the soil, climate, species composition and topography.The strata are: the tree layer, shrub layer and herb layer.
Among the different methods of studying vegetation, we used the phytosociological or stigmatist method [1].
The survey includes the list of all species and for each one with its rating of the abundance-dominance, socialbility and reliability.This minimum area [17] depends on the number of annual species at the time of survey and therefore the vagaries of rainfall and operating conditions [18].
For our case, the minimum area for Zarifet and Ghazaouet stations is 128 m 2 and for Beni-Saf, Aïn-Fezza, Nedroma and Ouled-Mimoun stations, the area is 64 m 2 .
The species recovery rate is theoretically defined as the percentage of the soil surface, which would be covered [17].This rate, variable from one station to another due to the vegetation control, remains very low.

Systematic Composition
Flora used for identification of taxa collected are: the New Flora of Algeria and Southern Desert Regions [11], the Mediterranean Flora [19], The Flora of the Sahara [20,21], the Vast Flora of France in colors [22] and flowers from Algeria [23].
The flora of the study area consists of 322 species or 10.26% of the flora of Algeria.They belong to the sub branches of gymnosperms and angiosperms, with 62 (42.18%) and 193 families (18%) types (Table 2).
Gymnosperms constitute 1.55% of the study area unlike with angiosperms which largely dominate.They constitute 98.45% of shrubland with 84.21% of Eudicots The plant diversity in the Tlemcen region (Northwest Algeria).and 13.93% of monocots (Table 1 and Figure 2).

Biological Types
For [25] analysis of biological type can give us information on the environment influence on the local vegetation.These biological types are considered to be an experience of coping strategy of flora and vegetation to environmental conditions and allow us to recognize, with respect to the "vascular plants", the following five main biological types: phanerophytes, chamaephytes, hemicryptophytes, geophytes and therophytes.
[26] Highlights the existence of a good correlation between biological types and many phenomorphological characters.
[10] Emphasizes on the abundant flora heritage value.Initiated studies, by [27], have focused on the variation of different ethological types in the sclerophyllous formations in the Mediterranean.
Many other works have been made in order to highlight on one hand the relationship between the distribution of biological types and environmental factors in particular the climate (temperature and rainfall) [28][29][30] and, on the other hand, the relations between the biological types distribution and "the altitude and the substrate nature" [31].

The Biological Spectrum
The biological spectrum [32] is the percentage of various biological types.
This percentage is substantially the same in regions far away geographically, which show an analogy with living conditions.
[26] Recommends the use of biological spectra as indicators of the distribution of morphological and probably of physiological traits.
Table 5 and Figure 4 show clearly that the distribution   He > Ge For all the stations studied, therophytes have the highest rate (39.41%), reflecting the high population pressure.
In addition to human impacts, the therophytisation traces its beginnings to the phenomenon of desiccation [12,15,[33][34][35][36].The latter present therophyty as a form of resistance to drought, and to drylands high temperatures.
Despite the therophytes importance, the chamaephytes keep a particularly important place.
For Zarifet and Ghazaouet stations, the rate of phanerophytes is low, despite a semblance of sylvatic environment.This is mainly due to the floristic richness of these stations, and the recent invasion by therophytes.For Beni-Saf station, the rate of phanerophytes remains very low; the results clearly show its degraded state.It is dominated by therophytes, chamaephytes, hemicryptophytes, phanerophytes and geophytes.Some authors like [37] explain the abundance of hemicryptophytes, in North Africa, a greater richness in organic matter in forest and elevation.This explains the low percentage, of hemicryptophytes in Ghazaouet station, Despite the therophytes importance, the chamaephytes keep an important place in the vegetation of the study area.They are most common in shrub land and are better adapted to drought [38].They are found in pastures and fields.This distribution is described by [31] in agreement with [28] and [39].
For our case, we recorded a percentage of 21.17% and among the species encountered, we have:

Rubia peregrina
They seem to increase in forest and high altitude.The dominance of hemicryptophytes is then an obstacle to the installation of phanerophytes.
Despite the low participation of phanerophytes species; they are dominant by their biomass, thus constitute the bushes and forests.They are abundant in the vegetation of Ghazaouet, Ouled Mimoun and Zarifet stations, which still bears witness to the existence of a forest and/or a pre-forest formation.
These are usually Quercetea ilicis species: We note that the absence of nanophanerophytes is certainly linked to severe erosion in the region but, especially, the power of the winds [40].
Finally, geophytes are everywhere; the least repre-sented with only 10.10%.Representation of the latter remains higher in the shrub land (10.77% in Nedroma) than in the pre-forest formations and forest (7.43% in Ghazaouet).
Among this group we have the Liliacaea, the Iridaceae, the Orchidaceae and Araceae represented by the following species: Scilla lingulata [30] Also found higher geophytes proportions in Mediterranean area than in steppe domain.
The origin of the extension of therophytes is due: ˗ Either to the adaptation to the winter cold stress [20,28] or to summer drought [29,34].˗ Or even to the medium disturbances by grazing, crops, etc. [41].Indeed, plant formations in dominant phanerophytic vegetal cover have the lowest recovery of therophytes while those, for which the phanerophytes rate is negligible, therophytes recovery is much higher.Similarly, [42] explain the changes of floristic composition and species biological cycle (after cutting the undergrowth of evergreen oak), by the increasing of the lower layers brightness level.

Disruption Index
The disturbance index (calculated according to [43]) quantifies the therophytisation of a medium.IP = Chamaephytes number + Therophytes number/Species total number For all stations this index remains high compared to [44] results in Tunisia, where he obtained 70% as high value.The chamaephytes and therophytes are the biological types that dominate in the region.This shows the anthropozoologic high pressure experienced by vegetation in the study area.
The disturbance index being about 57% for the entire study area, this shows clearly the sharp decline (Table 6).

MORPHOLOGICAL CHARACTERIZATION
The sharp deterioration affects species regeneration.The non-regenerating perennial causes changes that give non-resilient paths, and also causes a change in potential output and the botanical composition [45].The vegetal cover is dominated by three vegetation types: woody perennials, herbaceous perennial and annual grasses.
The morphological point of view, the vegetation of the study area is marked by heterogeneity between woody and herbaceous species and between perennials and annuals.The annual herbaceous species are dominant with a percentage of 50.80%.The herbaceous perennials come in second with 25.72%.In third place we find the woody perennial with a percentage of 23.47% (Table 7) and (Figure 5).
The intense human impact, which the forests of the region continue to suffer, results in the invasion of therophytes, which are typically annual herbs.Thus, the harsh conditions favor the development of short-cycle herbaceous species at the expense of woody perennials generally more demanding in water and nutritional needs.

STRATIFICATION
At the study area we have the herbaceous layer, which dominates with a percentage of 75.45%, then the shrub layer with 14.67% and finally the tree layer with a small percentage that is of the order of 9.88% (Table 8).
The herbaceous layer is generally formed by therophytes which are annual grasses in general (Figure 6).

BIOGEOGRAPHIC CHARACTERIZATION
The study of the Mediterranean basin flora is of great  Uncertainties remain for some species that are currently having an extension of their ranges.
The distribution of different species surveyed, by phytogeographical element, is very heterogeneous.˗ The endemism rate is relatively low with (5.06%).
The endemic North African species outnumber the Algerian-Tunisian and/or Algerian-Moroccan species.

CONCLUSIONS
The Tlemcen region is determined by a remarkable plant biodiversity influenced by many environmental stresses (drought, human action, overgrazing, etc.) which makes it integral part of the Mediterranean.
From the results obtained, we can conclude that all the studied formations are characterized by a dominance of therophytes.The intense human impact, experienced by the vegetation in the area, ends by an invasion of mainly therophytes.The latter characterize the group of Stellarietea Mediae, resulting in a homogenization and trivialization of most floristic formations of this region.Indeed, plant formations in dominant phanerophytic vegetal cover have the therophytes lowest recovery while those for  interest due to its richness, its high rate of endemism, its diversity related to the heterogeneity of historical, paleogeographic, ecological and geobotanical factors which determine it; as well as the ancient human pressure impact [39,[46][47][48].which the rate of phanerophytes is negligible, the therophytes recovery is much higher.The disturbance index being about 57% for the entire study area, this shows clearly the sharp deterioration.
From the morphological point of view, the study area vegetal formations are marked by heterogeneity between woody and herbaceous species and between perennials and annuals.The annual herbaceous species are dominant with a percentage of 50.80%.The herbaceous perennials come in second with 25.72%.In third place we find the woody perennials with 23.47%.
From the phytogeographical point of view, the Mediterranean element is the most dominant with 43.58%.
Finally, conservation of natural heritage remains a major initiative to preserve the region plant biodiversity against a regression which may become irreversible in the near future.
In this regard, Algeria, as all Mediterranean countries, has long been involved in the preservation and conservation of biodiversity policy through the creation of several national parks.Currently, Algeria has eight national parks that include all original landscapes and where are the main hot spots of plant biodiversity in the country [49].
Meanwhile, several research works, mainly focused on the inventory and mapping of this phytobiodiversity, have been done in these hot spot.Among these works, we mention those of [50] in Chrea National Park, [51] and [52] in El-Kala national park, [53] and [54] in Tlemcen National Park.All these works have stressed the importance of such an inventory in the sound management of natural ecosystems.Indeed, several authors suggested that the conservation and enhancement of a natural ecosystem requires a good knowledge of its biodiversity [49,55].Many of these works in these ecosystems have emphasized the rich flora of these environments and have shown a variety of endemic and/or rare species to be placed in conservation priorities.They also discussed the degradation advanced state of these natural ecosystems which is mainly attributed to the combined action of man and his animals (grazing).

Figure 1 .
Figure 1.Location of study sites.

Figure 3 .
Figure 3. Composition of the flora by family.
of biological types in the vegetation in the same station and between stations is heterogeneous: ˗ Aïn-Fezza and Ghazaouet stations follow the pattern: Th > Ch > Ph > He > Ge ˗ Ouled-Mimoun station follows the pattern: Th > Ph > CH > He > Ge ˗ Beni-Saf station follows the pattern: Th > Ch > He > Ph > Ge ˗ Nedroma station follows the pattern: Th > Ch > He and Ph > Ge ˗ Zarifet station follows the pattern: Th > Ch > Ph > He and Ge ˗ The study area follows the pattern: Th > Ch > Ph >

Table 1 .
The rates of angiosperms (Eudicots and Monocots) and gymnosperms.

Table 2 .
Composition in families, genera and species of flora.

Table 3 .
Inventory of families as a percentage (Study sites).
Figure 4. Percentage of biological types.whichvariesbetween 1.23% and 4.57%.For Aïn-Fezza, Ouled-Mimoun, Nedroma and Zarifet stations we see a very small percentage of hemicryptophytes although these stations are in a high altitude.Beni-Saf station has a high percentage of hemicryptophytes despite a low altitude.Among the species encountered, we have:

Table 7 .
Percentage of morphological types in the study area.

Table 9 and
Figure 7 hereafter show that: ˗ The Mediterranean native element is by far the largest with (43.58%).It is represented by the therophytes (14.61%) and by the woody phanerophytes (7.30%) and chamaephytes (8.63%).

Table 9 .
Biogeographic types with species number and percentage.