Impact of Anthropogenic Disturbance on Vegetation Structure of El-Maktala Coastal Land, Egypt

MATERIALS AND METHODS

Study area: El-Maktala region is located between latitude 31°33'North and longitude 26°10'East. It lies 140 km after Matrouh and 90 km before El-Sallum in the North Western Coast. Geomorphologically, the Sidi Barrani area is located near the Mediterranean Sea about 95 km east of the border with Libya and about 420 km west of Alexandria. El-Maktala sector comprises a vast area of fertile land (about 80 km²) with a more or less relatively dense cover of natural vegetation⁸.

Vegetation analysis: To estimate the vegetation structure in EL-Maktala coastal land, 12 stands were chosen to represent different plant habitats. A total of 12 stands were selected for the study of the vegetation of EL-Maktala coastal land during the summer season of 2018. In each stand, three quadrates were chosen (quadrate area = 10×10 m = 100 m²). Vegetation cover was measured using visual estimation. Recorded plant species in all localities were identified and life span was documented according to Boulos⁹. Life form and floristic category were recognized^9,10. Shannon-Wiener diversity index (H'), Relative equitability or evenness (E) and Simpson indices were calculated¹¹. Similarity Sorenson index was calculated¹². The vegetation quality index is valuable in determining the sensitivity of an area to desertification^13,14 in terms of four indicators namely: Vegetation cover, drought resistance plants, plant species that tolerate erosion and grazing risk¹⁵.

Soil analysis: Many soil factors were examined to determine the characteristics of the soil in the study area. From each stand, three soil samples were collected and merged to form a homogeneous and representative sample of a single locality. Fourteen soil factors were analyzed: Soil texture (sand, silt and clay), pH, electrical conductivity, magnesium, calcium, sodium, potassium, chloride, calcium carbonate, sulfate and organic carbon content. Soil texture was determined¹⁶ using a pipette method. Digital portable pH and EC meters were used to calculate pH and electrical conductivity (EC). Magnesium and calcium were determined using a titration method¹⁷. A flame photometer at wavelengths of 589 and 767 nm was used to determine sodium and potassium, respectively¹⁶. Chlorides and calcium carbonates were determined using a titration method¹⁷. Sulfates were determined¹⁶ using the turbid metric method. Organic carbon was determined using a titration method¹⁷.

RESULTS

Floristic composition: A collection of 27 plant taxa, belonging to 16 families, was recorded in El-Maktala coastal land. The most represented plant families were Poaceae, with 5 (18.5%), Asteraceae with 4 (14.8%), Fabaceae and Chenopodiaceae with 3 (11.1%), each them. Thirteen families (Amaryllidaceae, Apiaceae, Boraginaceae, Cistaceae, Brassicaceae, Euphorbiaceae, Nitrariaceae, Polygonaceae, Rubiaceae, Solanaceae, Thymelaeaceae and Zygophyllaceae) were represented by one species shown in Appendix 1 and Fig. 1.

Fig. 1:

Number of species distributed across different families recorded in El-Maktala coastal lands

Regarding the life span of the listed species, most of them are perennials (26 species) and one annuals species (Appendix 1). Comparing species according to their life form, we found approximately 63% chamaephytes, 15% hemicryptophytes, 11% phanerophytes, 7% geophyte and 4% therophyte in Appendix 1 and Fig. 2. Concerning a phytogeographical region, Mediterranean geo elements was the most common floristic category (13 species, 48%), followed by Saharo-Arabian (6 species, 22.2%), Mediterranean, Saharo-Arabian (3 species, 11.1%) and Saharo-Arabian, Sudanian (2 species, 7%). Mediterranean-Eurosiberian, Saharo-Arabian, Irano-Turanian and Mediterranean, Irano-Turanian. were represented by one species, respectively in Appendix 1 and Fig. 3.

Fig. 2:

Chorotypes of the species recorded In El-Maktala coastal land

Fig. 3:

Life forms of species recorded in El-Maktala coastal land

Classification: A data of 12 stands of vegetation occupying El-Maktala coastal land was analyzed using TWINSPAN to classify the stands at the fourth level into five groups labelled (A-E) in Fig. 4 with-set each sample group comprising a set of stands with greater homogeneity of vegetation, each group being characterized by indicator species, identified by TWINSPAN for each group at each level of hierarchical classification.

Group (A) consisted of three stands with twelve species. The indicator species of this group was Inula crithmoides, whereas, the dominant one was Ononis vaginales (I.V. = 66.7). Group (B) comprised three stands with nine species, the indicator species of this group was Suaeda vera, whereas, the dominant one was Salsola tetrandra (I.V. = 80.8). Group (C) has three stands with twelve species. The indicator species of this group was Euphorbia paralias whereas, the dominant one was Ammophila arenaria (I.V. = 96.7). Group (D) encompassed two stands with ten species. The indicator species of this group was Pancratium maritimum whereas, and the dominant one was Nitraria retusa (I.V. = 63.7). Group (5) is represented by one stand with five species. The indicator species of this group was Pancratium maritimum, whereas, the dominant one was Euphorbia paralias (I.V. = 44.5) (Appendix 1).

Diversity and vegetation quality index: The average of species richness, Shannon index (H), Shannon index (E) and Sampson Index (D) were 4, 0.07, 0.02 and 0.02, respectively. Sorenson’s coefficient (CC) was 0.44. The vegetation quality index (VQI) is valuable in determining the sensitivity to desertification (Appendix 1). The study showed that coastal land is highly sensitive to desertification each has a vegetation quality index (VQI) of 1.38 in Table 1.

Soil characteristics: Soil samples were taken at a depth of 0-30 cm in the studied localities and 14 soil factors were analyzed. Moisture, pH and EC values ranged between 1.17-3.91, 7.5-7.72 and 0.027-1.3 dS m^–1, respectively. Calcium, magnesium, sodium and potassium contents ranged between 1.2-3.9, 0.72-2.5, 1.11-3.3 and 0.2-0.66 meq L^–1, respectively. Chloride, sulfate and calcium carbonate contents ranged between 2-11 meq L^–1, 0.23-0.96 meq L^–1and 53-95%, respectively. Organic carbon, clay and silt contents in all soil samples were less than 0.04, 4.55 and 50.5%, respectively. In addition, sand contribution in all soil samples was more than 25.4% in Table 2.

Impacts of environmental factors on the distribution of plant communities in the studied localities: The distribution of the studied localities and recorded plant species and their relationships to environmental factors are illustrated in Fig. 5. CCA bio lot showed the relations between vegetation structure and environmental variables along with EL-Maktala coastal land. These arrows of environmental variables point to the maximum change of that environmental variable across the diagram. Its length is proportional to the rate of change in this direction, environmental variables with long arrows are most strongly correlated with the ordination than those of short arrows and so more closely related to the pattern of variation in species distribution in the ordination diagram.

Fig. 4:

Two Way Indicator Species Analysis (TWINSPAN) dendrogram of 12 stands based on the importance values of 27 perennial plant species in the study area

Biplot of the species revealed that several species showed a close association with CaCO₃ and sand, among them were Lotus polyphyllus, Ammophila arenaria, Euphorbia paralias and Elymus farctus. Other species showed a clear association with SO₄^–2 and organic carbon, of these species were Helianthemum lippii, Ononis vaginales, Hyoseris radiata and Retama raetam. However, Nitraria retusa, Zygophyllum album, Lycium shawii, Aeluropus lagopoides were found to be related to Ca⁺², Mg⁺², Na⁺, Cl^– and moisture content. Meanwhile, Thymelaea hirsuta, Atriplex halimus and Suaeda vera were affected with EC, K⁺, silt and clay.

Fig. 5:

CCA biplot showing the distribution of the studied localities and the recorded plant species as well as their relationships to environmental factors

The triangles represent species and the arrows represent environmental variables. Arrow length expresses the relative importance of an environmental variable. Dropping perpendicular to the arrows from each of the species indicates the species' relative position along the ecological gradient represented.

DISCUSSION

The present study provides an insight into the floristic composition, life-form, chorotype and community structure concerning edaphic variables of El-Maktala coastal land, Egypt. In El-Maktala coastal land, 27 plant species belonging to 16 families were recorded. Among them, Asteraceae, Poaceae and Fabaceae were the most frequent families. The vegetation of the study area exhibited the characteristics of the Mediterranean chorotype. The life form spectra provide information that may help in assessing the response of vegetation to variations in environmental factors⁸. The present study demonstrated that the dominancy was for chamaephytes over the other life forms which coincided with the study¹⁸ which seems to be a response to the hot-dry climate, topographic variation and biotic influence. Chamaephytes was the abundant life forms in the studied area coincided with⁸ and formed about 70% of the vegetation.

Species richness, which refers to the number of various plant species in the stands, is one of the most important indices of species diversity. In the studied stands, the average of species richness recorded three species, which is a low number. This could be due to a variety of factors, including the severe environment and climate that characterize the study area, which may be an obstacle to the growth of some plant species. Species evenness is a description of the distribution of species abundance in a community. The average of species evenness was 0.7. Species evenness is measured on a scale of 0 to 1, with 0 representing the lowest evenness (one species has 100% coverage) and 1 representing the highest evenness (coverage is evenly spread among some species). This may be due to the presence of a very dominant species in a community causing the less competitive species to be suppressed¹⁹. Shannon index depends strongly on species richness¹⁰. Simpson index is not a very intuitive measure of diversity since higher values indicate lower diversity²⁰.

Classification of the vegetation resulted in 5 vegetation groups associated with edaphic factors, which play a significant role in the distribution of the different vegetation groups. Vegetation along with the coastal lands, in general, is not constant; varying from year to year, depending upon the moisture level⁸. The establishment, growth, regeneration and distribution of plant communities in the coastal lands are controlled by many factors such as geographical position, physiographic features and human impacts^21-23. The differences between the recorded vegetation groups and diversity may reflect the correlation with the environmental gradients. Under conditions of low and irregular rainfall prevailing in the study area, local topography is one of the overriding factors controlling sedimentation and water redistribution with the local landscape²⁴.

In this study, CCA results highlighted that soil chemical features (organic matter and CaCO₃ content), distance from the coastline and anthropogenic factors (overgrazing, trampling and urbanization) are the main significant explanatory variables that govern the floristic composition and patterns in the study area. In general, topographic and soil factors are complementary to and/or consequences of anthropogenic activities²⁵, nonetheless, plants that occur only in specific environments, such as the Mediterranean coastal lands, are more prone to suffer as a result of human-related disturbances than those with a wide distribution and ecological range^25,26. By increasing the distance from the coastline, the content of soil organic matter increases and CaCO₃ content decreases; these general relationships along dune types are well known for a long time²⁷. The high concentration of organic matter, particularly in stabilized dunes, is evidence of soil development, which is the main cause of the plant succession in addition to its main role as a reservoir for the essential elements^28,29 also, high concentrations of CaCO₃ in foredunes confirm its role in the establishment of pioneer communities in addition to being considered as a predictor for the development of stabilized inland dunes²⁹. In addition to the environmental variables considered in this study, other environmental factors have significantly contributed to the explanation of coastal vegetation and should be considered for further studies, such as pH, electric conductivity, salinity, sorting, mean grain size, shoreline trend, erosion and wind-related variables³⁰.

CONCLUSION

The violation and destruction of wildlife have increased, therefore, preserving it along with general biodiversity has become an urgent necessity. Current results highlighted the importance of soil variables (e.g., organic matter and CaCO₃ content) and human impacts (constructions of roads and urbanization) on vegetation structure and quality, also life forms plant species composition in coastal land.

SIGNIFICANCE STATEMENT

By increasing the intensity of destruction, the number of species would be decreased and the community structure and species composition would be changed. Also, anthropogenic disturbance decreased the amount of organic matter (carbon and nitrogen) according to the degree of man-made disturbances. Therefore, a comprehensive program should be considered for coastal lands.