ECOLOGICAL CHARACTERISTICS OF EXTREME HABITATS IN EASTERN PROVINCE OF SAUDI ARABIA

Extreme habitats, in three sites (1-3), located in the Eastern Province of Saudi Arabia, were investigated. Two sites (1&2)are located at the Arabian Gulf shoreline; representing the habitats of littoral sabkha /salt marsh, and those of mangrove swamps; respectively. The third site (3) is located, landwards, towards the Dahna sand, representing the habitats of sand plains. The three sites are characterized by along dry season extending from April to December (as indicated the climate diagram); while the calculated index of aridity classify the climate, of the studied sites, as ''arid''. The halophytic species: Halocnemum strobilaceum, Arthrocnemum macrostachyum and Salsola drummondii characterized the littoral sabkha habitats; whereas the grey mangrove plant Avicennia marina characterized the seaward zone, in the mangrove swamp habitats. Two xerophytic species: Haloxylon persicum and H.salicornicum characterized the sand yplain habitats. Plant samples and their associated soils, were collected during wet and dry seasons. The plant water status (expressed as % relative water content and succulence), total ash and ionic composition of plant species were determined; and results indicated seasonal changes. Some soil parameters were determined, as important edaphic features of the habitats. Results of soil moisture, pH, electric conductivity (EC), CaCO3, organic carbon, and total nitrogen showed significant variations between the habitats in the studied sites(1-3). Correlation and linear relation were obtained between the contents of mineral ions in plant species and those in their associated soils. Characteristics of habitats are discussed.