Australian Journal of Basic and Applied Sciences, 3(1): 167-176, 2009 ISSN 1991-8178 Corresponding Author: Ashraf M. Youssef, Botany Department, Faculty of Science, Ain Shams University, Cairo, Egypt 167 Vegetation Analysis along Alamain- Wadi El- Natrun Desert Road Ashraf M. Youssef, Amal A. Morsy, Hosny A. Mossallam and Ahmed H. Abd Al-Latif Botany Department, Faculty of Science, Ain Shams University, Cairo, Egypt Abstract: This work was conducted along Alamain- Wadi-El Natrun desert road of the western desert in Egypt. The study area extends about 133 km from Marina– Alamain (on the Mediterranean coastal region) in the north to Wadi El-Natrun in the south. The main objective was to investigate the effect of environmental characteristics on the importance value indices and size structure of species and density per hectare. In the two different studied habitats: 1) sandy flat and 2) non-saline depression habitats. The phytosociological study of this road was based on the analysis of vegetation in 50 stands using Braun-Blanquet technique. Out of fifteen perennial species along the study area, three species named Cornulaca monacantha , Artemisia monosperma and Anabasis articulata, had higher species density, respectively. The sandy flat habitat indicated the highest density of Artemisia monosperma and Asphodelus microcarpus species (1740 and 1567 ind./ha, respectively), while in the non-saline depression habitat, Fagonia glutinosa had the lowest population density (125 ind./ha). Data of the present study revealed that annuals had the highest contribution than pernnials.Regarding the life forms spectra, therophytes have the highest records of 43%. Anabasis articulata recorded the highest (I.V) and frequency values ( 49.3 and 60 percent ) Key words: Vegetation, species density, importance value, Alamain, Western Desert, Wadi-El-Natrun INTRODUCTION Vegetation has been widely used to describe habitat characteristics, water quality and make predictions about the presence and composition of the surrounding communities (Appelgren and Mattila, 2005). In Egypt, desert vegetation is the most important and characteristic type of natural plant life. It covers vast area and is formed mainly of xerophytic shrubs and sub-shrubs (Abd El-Ghani et al., 2003). Annual plants represent 50- 60% of the desert vegetation during the rainy season (Kassas, 1964). Change in the existent components of a natural ecosystem, especially plants and soil, leads to gradual variations in the shape, composition and structure of such communities. Therefore, studying the classification and the inter-relation between the different plant communities in response to the environmental factors are demand (Jafari et al ., 2003). Inter-relationships between plant communities and environmental factors are complex, reflecting simultaneous changes in factors such as ground-water depth, soil moisture, soil stability and salt content (Zhang et al., 2005). The effects of environmental factors on plant communities have been the subject of many ecological studies. Jafari et al . (2004) revealed that the vegetation distribution pattern in rangelands of Yazd Province (Iran) was mainly related to soil texture and moisture contents. Youssef et al. (2009) stated that the plant species is generally determined by climate, geomorphology and influenced by soil conditions during their studies on vegetation of the coastal areas in Saudi Arabia. However, Zegeye et al. (2006) showed that the interdependency of vegetation type and soil chemical properties lead to a variety of species, vegetation types and distribution of plant communities. The Western Desert of Egypt extends over more than 1000 km throughout the country and covers approximately two-thirds of the Egyptian territory. One of the most important features is the uniformity of the surface of this area compared with other parts of Northern part of Egypt. The interior plateau is flat; there is nothing but plains or rocks either bare or covered with sand and detrital material (Abd El-Ghani, 2000 and Ayyad et al., 2000). Zahran and Willis (1992) divided the Western Desert into three main regions: 1) the Western Mediterranean coastal belt, 2) the inland oases and depressions and 3) the Gebel Uweinat. The study area lies in the zone of semiarid region and its temperature regime is characterized by mild winters and long dry hot summers. Youssef and Al-Fredan (2008) stated that the occurrence, distribution and composition of plant species form the different ecological groups, are related to the degree of soil salinity and/or heterogeneity of substrate in the stabilized sandy substratum which supported the recorded types of halophytic and/or xerophytic species.