Biol Fertil Soils (1987) 3:75-80 Biology and Fertility of Soil s © Springer-Verlag 1987 Seasonal differentiation of soil mesofauna in a fittoral dune of the Egyptian Mediterranean coast* S.I.Ghabbour 1, J.P. Cancela Da Fonseca 2, and W.Z.A. Mikhail 1 1 Department of Natural Resources, Institute of African Research and Studies, Cairo University, 12613 Giza (Cairo), Egypt 2 Laborattoire de Biologie Vrgdtale et d'Ecologie Forestirre, Route de la Tour Ddnecourt, F-77300 Fontainebleau, France Summary. Soil mesofauna (sensu Ghilarov, i.e., larg- er than 1 mm) was sampled from under four shrub species (Lygos raetam, Thymelaea hirsuta, Lycium shawii, and Josonia candicans) growing on the littor- al oolitic sand dunes at Gharbaniat, 53 km W of Alexandria, Egypt, for a period of more than 30 months, spanning 3 years. Population density (PD) was calculated in relation to area of shrub canopy. Seasons were considered, according to the prevail- ing climatic conditions as well as to earlier physiolog- ical studies on the animals concerned, as: four "winter" months, four "summer" months and two months for each of the transitional seasons "spring" and "autumn". The PD values obtained for each season thus defined were combined for the 41 taxa that were sampled. The table of these data was treat- ed by correspondence analysis (CA) and ascending hierarchic classification (AHC), by the Roux DATA- VISION programme (suitable for Apple). Results from such treatment show that fauna as related to shrub species are differentiated along the first fac- torial axis, while as related to seasons they are differ- entiated along the second axis. Taxa common to all shrubs and to all seasons are centrally placed and cause some confusion in the resolution. Summer taxa are more distantly placed than those related to the other three seasons. Fauna under Lygos is rich- er, more diverse, and more complementary as re- gards trophic levels (with predators), and could prob- ably be the source for replenishing the fauna of the other shrubs at all seasons. The AHC method did not show a similarly clear differentiation. * Dedicated to the late Prof. Dr. M.S. Ghilarov Offprint requests to: S.I. Ghabbour Key words: Mariut region-Correspondence analysis - Heterogamia syriaca, Lygos raetam - Predators Seasonal variation in population density and species structure of soil fauna in deserts has seldom been studied, although sampling may have been seasonal. The development of sophisticated computer meth- ods allows us now to resolve this question with great- er confidence and to discern patterns more subtle than hitherto accepted. The present paper describes the application of some of these methods to data of population density of soil mesofauna in the littoral sand dunes at Gharbaniat, in the northwestern Medi- terranean coastal land of Egypt, 53 km W of Alex- andria. Material and methods The Gharbaniat site. The Gharbaniat site is situated in the Mariut coastal region, extending about 100 km W of Alexandria, as the eastern part of the western Mediterranean coastal desert between Alexandria and Salloum on the Libyan border, for a length of about 550 km. The coastal land is considered as extending about 30 km inland. Rainfall varies from 130 to 150 mm/year, but during the past decade it has not exceeded 110 mm. Most of the rain fails in December and January. Soils are calcareous clay loam or sandy loam with admixtures of siliceous sands. In the littoral dunes, soils are almost purely CaCO 3 (80%-90%), made up of oolitic limestone, loose on the surface and consolidated underneath. The landscape is dominated by four prominent ridges running parallel to the coast and enclosing between them longitudinal plains (de- pressions). Each ridge is higher and more consolidated than the previous one as we go inland. The littoral (first) ridge is about 20-22 m above sea level at its highest point, with a maximum width of 1/2-1 km. Vegetation consists of sparse shrubs and sub- shrubs, conserved to some extent by the Bedouins for quail trapp-