This investigation was carried out during the period extended from spring 2011 to autumn 2012 at Sidi-Barrani in the North Western Coast of Egypt under rainfed conditions. The objective of this investigation was to study the natural vegetation qualitatively and quantitatively in relation to the effect of some ecological factors, i.e., plant communities and growth seasons on some range measurements, i.e., botanical composition, plant density, coverage, frequency, importance value, foliage yield and nutritive value of some perennial species. Thirty-eight plant species belonging to 16 families were found; the highest number of plant families, number of plant species and palatable plant species were obtained under Artemisia herba-alba community. The highest values of plant density, coverage % and forage yield were recorded under A. herba-alba community in spring season during both years. Meanwhile, the lowest values of all studied traits were recorded under Anabasis articulata community in autumn season.Significant differences were found between plant communities, growth seasons and their interaction.Among perennial species, the highest figure of importance value (IV) was contributed by A. articulata, A. herba-alba and Gymnocarpos decandrum in both years. While, Trigonella stellata and Aegilops kotschyi have the highest values (IV) among the annual species in the first year. Meanwhile, Hippocrepis bicontorta, Scorpiurus muricatus gave the highest (IV) during spring season in the second year.Highest digestible crude protein percentage (DCP) was recorded in Helianthemum lippii species followed by A. herba-alba. The highest TDN % were achieved by Noaea mucronata and G. decandrum. A. herba-alba and H. lippii gave the maximum values of digestible energy (DE), metabolized energy (ME) and net energy (NE). Deverra tortuosus recorded the highest value of gross energy (GE).ª 2014 Production and hosting by Elsevier B.V. on behalf