VEGETATION ANALYSIS OF THE IRRIGATION AND DRAINAGE CANALS IN EASTERN SAUDI-ARABIA

The present study analyses the vegetation along the irrigation and dra inage canals in Al-Hassa Oasis, Eastern Saudi Arabia. A total of 98 pl ant species were recorded. The annuals decrease, and the biennials and perennials (many are rhizomatous) increase along the moisture gradien t from the terraces to the free-water zone. This appears to be correla ted, at least partly, with the instability of the substratum along the banks. Twelve vegetation clusters were identified after application o f the TWINSPAN procedure. The most important are the cluster character ized by Suaeda aegyptiaca, Phragmites australis and Salsola vermiculat a, and that dominated by Phragmites australis. The identified vegetati on clusters were compared with the plant communities of the irrigation and drainage canals in the Nile Delta region.