Available online 22 May 2015
Original research article
Effect of the recent land use on the plant diversity and community structure of Omayed Biosphere Reserve, Egypt
- Under a Creative Commons license
The present study aims at describing and analysing the floristic composition and vegetation types, as well as determining the effect of recent land uses on the vegetation structure. It aims also at identifying the alien plants species and elucidating the impact of these species on the plant diversity and community structure of the study area. One hundred and ninety stands were selected monthly for this study, 145 species were recorded (69 perennials and 76 annuals) related to 83 genera, 40 families in 9 identified habitats in El-Omayed Biosphere Reserve (coastal sand dunes, salt marshes, saline depression, non-saline depression, inland ridges, inland plateau, irrigation canals, road sides and cultivated lands). Therophytes were the most represented life form. Three habitat groups resulted after the application of TWINSPAN and DCA as classification and ordination techniques: 2 represented the natural habitats and one represented the urban and cultivated habitats. Group I represented coastal dunes and salt marshes GII: saline depressions, non-saline depressions, inland plateau and inland ridges and GIII: irrigation canals, road sides and cultivated lands. Coastal dunes had the highest species richness (α-diversity), followed by cultivated lands, while inland plateau had the lowest; but saline depressions had the highest species turnover (β-diversity). Non-saline depressions had the highest relative evenness, while saline depressions had the highest relative concentration of dominance. Coastal dunes had highest values of calcium carbonates and calcium ions, and salt marshes had the highest salinity, pH, potassium and sodium contents, but cultivated lands had the highest values of silt, clay and organic matter. The diagram resulting from CCA showed an influence of most soil variables, except nitrogen, calcium and potassium. Twenty two species were recorded for the first time in the study area. The recent land use (overgrazing, wood cutting and collecting, construction of summer resorts and irrigation canals and agricultures) led to the emergence of new invasive species, which may severely affect the plant diversity and community structure of this hot spot of biodiversity in Egypt.
- El-Omayed Biosphere Reserve;
- Alien species;
- Species diversity;
In semi-arid Mediterranean ecosystems, the scarce and irregular rainfall, long dry and hot summer, and man-mediated degradative activities may synergistically act as driving-forces for the promotion of the desertification process (Azcón-Aguilar et al., 2003). Degradation of natural plant communities, in terms of population structure, successional patterns or species diversity, is known to occur concomitantly with the degradation of physico-chemical and biological soil properties (Requena et al., 2001).
Alien plants species are species that are introduced as a consequence of human activities to new geographic areas, where they become established and then proliferate and spread, to the detriment of human interests and natural systems. These impacts are not all negative and alien plant species bring both costs and benefits to local people. Costs are incurred if the alien species inhibit the effective functioning of the local social and ecological systems, such as when alien species become weeds within agricultural systems, inhibit vital ecosystem functions or affect animal or human health (Pimentel et al., 2001). Apart from alien species threat to biodiversity and ecosystem services, alien species have a significant socio-economic impact, they reduce yields from agriculture, forestry and fisheries, decrease water availability, cause costly land degradation, block transport routes and contribute to the spread of disease (Garcia-Llorente et al., 2008).
Man-made habitats, as in reclaimed desert lands, represent species-rich environments (Wittig, 2002) due to habitat heterogeneity, frequent and diverse disturbances creating mosaics of different successional stages, and immigration of alien species (Pyšek et al., 2002). This human interference causes the invasive species to replace the wild species in these reclaimed areas (Baessler and Klotz, 2006), which are considered to be transitional habitats between the old cultivated land and desert. The invasive species in the new agricultural lands cause serious problems that require attention to be paid to the negative impacts of plant invasions on ecosystems and gene pools (Hegazy et al., 1999).
El-Omayed Biosphere Reserve (OBR) is the only protected area in the northwestern Mediterranean coast. It joined the world network of biosphere reserve in 1981 and was declared as a protected area by Prime Minister Decree in 1986. Being a biosphere reserve, the area is expected to serve as a site for sustainable development of natural resources by rationalizing ecotourism, rangeland management, propagating multipurpose woody species, and promoting local industries. It also has an important function in long-term ecological monitoring.
El-Omayed Biosphere Reserve (OBR) was a representative area of the northern Mediterranean coast of Egypt which has a variety of development and conservation activities. The pressure of land use, coupled with a severe environment and uncertainly of rainfall, has resulted in an advanced stage of desertification. Studies on the distribution of plant species and communities in the different habitats has been reported by Migahid et al. (1971), Ayyad (1976), Abdel-Razik (1976), (Shaltout, 1983 and Shaltout, 1985), Abdel-Razik et al. (1984), Kamal (1988), Shaltout and Ayyad (1994), Ayyad and Fakhry (1996), Shaltout and Al-Sodany (2002). Moreover, it was subjected to many human-induced disturbances (the construction of irrigation canals and roads, the construction of tourist resorts on the coastal ridge, the implementation of rain-fed plantations, quarrying activities inside the reserve). These impacts may directly result in the introduction and establishment of alien plant species affecting the vegetation structure and biodiversity.
The present study aims at describing and analysing the floristic composition and vegetation types, as well as determining the effect of recent land uses on the vegetation structure. It aims also at identifying the alien plants species and elucidating the impact of these species on the plant diversity and community structure of the study area.
2. Material and methods
2.1. Study area
OBR is located in the western Mediterranean coastal region of Egypt, at 80 km west of Alexandria ( and ). It extends about 30 km along the Mediterranean coast from west El-Hammam to El-Alamein with a width of 23.5 km to the south. Its landscape is differentiated into a northern coastal plain and a southern plateau. The coastal plain is characterized by alternating ridges and depressions running parallel to the coast in an east–west direction. This physiographic variation distinguishes seven types of habitats, (coastal sand dunes, saline depressions, non-saline depressions, inland ridges, inland plateau, inland siliceous deposits, and rain-fed farms), each with its characteristic flora and vegetation. In the non-saline depressions, man-made rain-fed fig and watermelon plantations are common in addition to grazing, intensive quarrying and irrigated land agriculture which is another potential activity that is introduced due to the extension of an irrigation canal from the Nile delta to the region and intensive establishment of resorts on the coastal dunes (Ghabbour, 2012).
Surface soil layers were loose and subject to active erosion and deposition creating micro-topographic variations, but below 25 cm, soils are often compact (El-Kady, 1993). The climate of this region belongs to the warm coastal desert climate; mean air temperatures varied from 13.6 to 27.2 °C, the warmest summer month (August) has a mean temperature less than 30 °C, and the coldest winter month (January) has a mean temperature above 10 °C. Mean air relative humidity varied from 56% to 87%. The rainy season begins during the second half of October and extends to the first half of May. Mean annual precipitation is 120 mm, recorded at an elevation of 10 m. Occasional short rainstorms occur mainly in winter. The ratio of annual precipitation to annual evaporation is between 0.03 and 0.2 (Agwa and Al-Sodany, 2003).
In the last few years, the study area had witnessed stresses on water resources that had led to undesirable consequences related to both its quantity and quality. Recently established summer tourism resorts along the coastal area have damaged the important freshwater aquifer (dune sand accumulation) near the coast. In addition, groundwater pollution either by salt-water intrusion or by sewage from septic tanks or landfills (from the resorts) had been noticed in some areas. The desert ecosystems were exposed to both natural (aridity and soil surface erosion) and human induced impacts (overgrazing, woodcutting, soil salinization, and the introduction or expansion of agro-forestry systems with multiple land-use to develop tourism, wildlife, hunting and sports) which either act in isolation or in combination with each other (Ahmed, 2009).