ANALYSIS OF RAUDHAS VEGETATION IN CENTRAL SAUDI-ARABIA

The present study analyses the vegetation of three raudhas in central Saudi Arabia (Kharj, Khuraim and Binban). Seventy-five stands were exa mined and the martrix of 68 species X 75 stands, based on species cove r data, was classified using TWINSPAN and ordinated using DCA. Eleven vegetation groups were generated: one dominated by Haloxylon salicorni cum and five dominated by Acacia spp. (A. iraquensis, A. elatior, A. s eyal, A. tortili-Ziziphus spina-christi-Rhazya stricta and A. abyssini ca). The Acacia spp. communities represent the climax stage of the xer ophytic vegetation in Saudi Arabia and have, in most cases, high speci es cover and low species diversity. Another five groups are dominated, fully or partly, by species that often inhabit disturbed areas (Proso pis juliflora, Heliotropium bacciferum-Tamarix arabica-Prosopis julifl ora-Pulicaria crispa, Ziziphus spinsa-christi-lagonychium farctum-Alha gi maurorum-Cynodon dactylon, Salsola imbricata and Bassia eriophora-C hloris virgata-Zygophyllum coccineum-Seidlitzia rosmarinus). Many of t hese groups have low species cover and relatively high species diversi ty. The effects of environmental factors and human impact on species d iversity and abundance of these communities were assessed. (C) 1996 Ac ademic Press Limited