This work is an evaluation of the plant diversity of the white Wormwood formations ( Artemisia herba-alba Asso.) in the steppes rangelands of the south-eastern zone of Sa ?da (municipality of Maamora, Western Algeria). For this purpose, twenty-one phytoecological statements are carried out on three sample stations: an exclosure station where the white Wormwood is well developed and two other stations not protected where in one, the white Wormwood is moderately degraded and in the other one, it is strongly degraded. The factorial correspondences analysis (FCA) and the ascending hierarchical clustering (AHC) carried out on the floristic and edaphic parameters measured on these stations led to a hierarchy of the ecological factors determining the diversity of the studied plant formations with white Wormwood. The vegetation studied is marked by the dominance of the therophytes, particularly in the third station (very degraded station), while the exclosure station is essentially characterized by a high recovery rate and an important phytomass.
The natural and ecological resources constitute a richness whose degradation represents a constraint to the human development, economics and a threat for social balance. The steppe vegetation plays a fundamental role in the structure and the running of the steppe ecosystem where it constitutes an expression of the biological potential. However, natural vegetable cover is subjected to a double stress edaphic and climatic, on the one hand and anthropic, on the other hand [
Among the characteristic plants of the steppe landscape, the white wormwood (Artemisia herba-alba Asso.) by morphological and physiological characteristics represents a species well adapted to the arid climatic conditions. The white wormwood steppes by their extent, their homogeneity and their pastoral interest, constitute the current facies of the steppe area in south of Oran (Western Algeria). The vast areas are covered by these facies north of chotts Ech-chergui and gharbi along a band of 250 km [
The knowledge of the natural vegetation as a reflection of ecological conditions must allow a preliminary diagnosis, which can direct improvement actions and development of the steppe region [
The study area is part of the high steppe plains of south oranians (municipality of Maâmora, Wilaya of Saida, west of Algeria). It is located between 0˚ and 1˚ longitude and 34˚ and 35˚ of northern latitude.
In accordance with the climatic data of the period 1978-2010 [
In this study area, three stations are selected for our investigations:
・ station 1: rangeland exclosure by the High Commission at the Development of Steppe (HCDS) since 2008, with a surface of 7000 ha, where the white wormwood is well developed (rate of total recovery = 59%, including 32% for the white wormwood);
・ station 2: rangeland of white wormwood fairly degraded (rate of total recovery = 26%, including 12% for the white wormwood), with a surface of 2700 ha;
・ station 3: rangeland of white wormwood strongly degraded, subjected to a strong anthropic pressure with a surface of 1600 ha (rate of total recovery = 14% including 8% for the white wormwood).
For the study of the vegetation, we adopted the method stigmatist of Braun Blanquet [
For each statement are noted the altitude, the rate of recovery and phytomass of the vegetation. The inventoried species are determined by using the flora of Algeria of Quézel and Santa [
The estimate of aerial phytomass is made, in each statement, by whole mowing of the aerial part of the vegetation on a surface of 1 m2, then brought back in paper bags to the laboratory for drying and weighing [
Three pedological statements were carried out in each station, on the level of each statement, the physicochemical analyses are carried out on taken samples of soil of the surface horizon, whose properties are often related to the human, agricultural or pastoral disturbances [
The indices of similarity of Sorensen and Jaccard are used to compare the similarity of the floristic composition of the three stations; the indices of diversity of Shannon and equitability are used to evaluate their specific diversity [
On
The floristic richness of arid region depends primarily on the annual species, environmental conditions and the correlation of the whole of the characters (climate, edaphic conditions and exploitation) [
From a point of view taxonomic, the inventoried species belong to 21 families (
two families adapt well in the arid and semi-arid areas, they are very widespread in the entire steppe and the Saharian Atlas [
The analysis of the biological spectrum of the vegetation shows the prevalence of the therophytes with a rate of 62% in the station 1, 64% in the station 2 and 67% in the station 3 (
The analysis of the phytogeographical spectrum shows the dominance of the species of Mediterranean affinity, they account 27% for the station 1, 23% for the station 2 and 19% for the station 3, reflecting the affiliation of the steppes studied to the Mediterranean region. This confirmation is consensual between the whole of the works on the North African steppes [
The global recovery is an important parameter state indicator of the vegetation and biodiversity [
respectively for the stations 2 and 3, of the
The phytomass varies also from a station to another (
The pedological analyses made on the soils of the study area show that the soil texture of the three stations is silt-sandy, these results are also obtained by Benabadji et al. [
The indices of floristic similarity of Sorensen and Jaccard are higher than 60% (
Profiles | Depth (cm) | Sand (%) | Slay (%) | Silt (%) | Texture | Moisture (%) | Salinity (mmhos/ cm) | Organic matter (%) | pH | Total limestone (%) | |
---|---|---|---|---|---|---|---|---|---|---|---|
Station 1 | R1 | 8 | 57 | 13 | 30 | Silty-sand | 5.8 | 0.03 | 1.84 | 8.9 | 14.7 |
R2 | 15 | 63 | 9 | 28 | 4.7 | 0.02 | 2.9 | 8.75 | 17.32 | ||
R3 | 10 | 54 | 9 | 37 | 5.1 | 0.07 | 2.6 | 8.85 | 17.32 | ||
Average | 11 | 58 | 10 | 32 | -- | 5.2 | 0.04 | 2.45 | 8.83 | 15.97 | |
Station 2 | R1 | 9 | 67 | 3 | 30 | Silty-sand | 3.8 | 0.04 | 2 | 8.88 | 14.53 |
R2 | 8 | 62 | 8 | 30 | 5.2 | 0.18 | 0.46 | 8.87 | 18.45 | ||
R3 | 7 | 62 | 10 | 28 | 3.5 | 0.04 | 1.7 | 8.7 | 16.81 | ||
Average | 8 | 64 | 7 | 29 | -- | 4.17 | 0.09 | 1.39 | 8.82 | 16.59 | |
Station 3 | R1 | 6 | 58 | 13 | 27 | Silty-sand | 3.1 | 0.47 | 1.78 | 8.88 | 19.27 |
R2 | 5 | 61 | 10 | 32 | 2.5 | 0.14 | 2.23 | 8.69 | 22.47 | ||
R3 | 7 | 62.5 | 11.5 | 25 | 3.2 | 0.22 | 1.9 | 8.74 | 25.43 | ||
Average | 6 | 60.5 | 11.5 | 28 | -- | 2.93 | 0.28 | 1.97 | 8.77 | 22.39 |
Species diversity and evenness of the three stations | |||
---|---|---|---|
Station 1 | Station 2 | Station 3 | |
Shannon diversity index (bits/individual) | 3.90 | 4.01 | 3.66 |
Equitability [E] | 0.86 | 0.88 | 0.81 |
Floristic similarity between the three stations | |||
Station 1 - Station 2 | Station 1 - Station 3 | Station 1 - Station 3 | |
Sorensen index | 0.80 | 0.70 | 0.69 |
Jaccard index | 0.89 | 0.68 | 0.75 |
the second station and 3.90 bits/individual for the first station. These values translate, in the three stations, a specific richeness stable of quantitative and qualitative a point of view. The values of the indice of equitability are comparable for the three stations (station 1: 0.86; station 2: 0.88; station 3: 0.81), thus representing an equal distribution of the species.
In the FCA carried out on the edaphic and floristic parameters of the three stations (
On the axis F1, two distinct groups separate. The formation of these two groups is supported by the ascending hierarchical clustering (AHC) carried out in parallel. The group 1 is represented by the stations 1 (st 1) which is an exclosure station where the wormwood is well developed and the station 2 (st 2) which is moderately degraded. These two stations are correlated with chamaephytes (Ch), hemicryptophytes (He), organic matter (OM), rate of recovery (Gc), phytomass (phyto), pH, soil depth (SDe) and moisture (Hu). We note that on this group emerged, the state of the plant cover in particular the global recovery and the phytomass reflect the slight improvement of the edaphic characteristics in both stations 1 (st 1) and the station 2 (st 2), which confirms that these two stations are more rich at least in floral point of view and have some edaphic characteristics better than those of the station 3 (very degraded station). This is in particular case about some parameters, namely the organic matter, the depth of the soil and the humidity.
The group 2, represented by the station 3, is correlated to therophytes (Th), clays (A), total limestone (CT), geophytes (Ge) and sands (Sa). All these variables represent indicators of degradation, as a result, consequence of the anthropic impact.
Besides, the axis F1 of the FAC indicates a regressive evolution of the environment, related to a gradient anthropic, expressed in positive side towards the negative side and inversely for the recovery and phytomass that translate a progressive evolution of the environment, in negative side towards the positive side of this axis.
The results obtained have allowed us to establish a preliminary assessment of the plant diversity of the steppe with the white wormwood of the municipality of Maâmora in the wilaya of Saida (west of Algeria). In fact, if we refer to the classification of Daget and Poissonet [
The synthesis and the exploitation of data relating to floristic settings and edaphic measures, carried out by the FCA and the AHC, highlight the impact of the anthropic action on the distribution of vegetation formations of white wormwood. The Asteraceae and Poaceae are the families that are most represented in the study area. The biological characterization shows the dominance of therophytes. For the phytogeographical characterization, it is the Mediterranean component which dominates all of the stations studied.
In the light of these results, we can focus on the interest and the constructive impact of the exclosure on the recovery rate of the vegetation, the floristic richness and the phytomass. The exclosure account among the efficient means and less costs for the rehabilitation of rangelands disrupted. Actions for conservation must be carried out to save this heritage which incurs major risks of genetic and biological collapse. These actions for the conservation of biological diversity should first and foremost focus on the safeguarding of ecosystems because the protection of species is illusory if we do not protect simultaneously their natural habitats [
Finally, the evaluation of plant diversity of white wormwood steppe ecosystem of the explored area as presented in this present work is preliminary and far from being exhaustive. In fact, we are projecting to extend it in space and time for a better characterization in order to identify more factors that govern the operation, evolution and dynamics of this ecosystem subjected to various offenses.
We thank the High Commission at the development of the steppe and the national office of meteorology of Saida to have provided us the necessary data to carry out this work.
SaidiAbdelmoumen,MehdadiZoheir, (2015) Evaluation of Plant Diversity in the Steppes of White Wormwood of the Region of Saida (Western Algeria). Open Journal of Ecology,05,491-500. doi: 10.4236/oje.2015.510040