Available online 22 May 2015
Open Access
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
Abstract
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.
Keywords
- El-Omayed Biosphere Reserve;
- Alien species;
- Species diversity;
- Vegetation;
- Habitat
1. Introduction
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).
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).
