FLORISTIC DIVERSITY, ECOLOGY AND HABITAT CHARACTERISTICS OF COMMUNITIES WITH BRASSICA TOURNEFORTII GOUAN IN NORTHERN OF SAUDI ARABIA

The present study aimed to identify the communities with Brassica tournefortii Gouan in Al-Jouf areas in northern Saudi Arabia, to determine the ecological amplitude of this species and soil factors controlling its distribution. The plant communities dominated by B. tournefortii were investigated in fifteen localities through 15 plots. In each plot the present species were recorded. Data were treated by multivariate analyses. Soils of each community were analyzed using eleven physico-chemical parameters. Analysis of variance and correlation coefficient were performed based on R software package. Three vegetation types have been recognized by the applications of Past program classification. 83 species have been observed. Canonical correspondence analysis demonstrated that soil parameters contributed significantly to the distribution of species. B. tournefortii dominated the communities in newly reclaimed lands, where it survived in sandy habitats. It is characterized by high competition with both cultivated plants and associated weeds. This paper represents a study of the diversity of B. tournefortii communities in Arabia Saudi. KeywoRdS Brassica tournefortii; plaNt aSSociatioNS; ecological gRadieNt; SpecieS RichNeSS; Soil chaRacteRiSticS. 2 Nagmouchi S. , alSubeie m. It is considered a weedy species in agricultural fields in parts of its native range (Ahmed et al., 2015; El-Saied et al., 2015), but it has also traditional dietary uses and economic value in regions where it is cultivated (Singh et al., 2015; Guarrera & Savo, 2016). It has been shown that allelopathy offers great potential to increase agricultural production, decrease the harmful effects of modern agricultural practices, and maintain soil productivity and a pollution-free environment for future generations (Abd El-Gawad, 2014). Winkler et al. (2018) showed that linking life-history strategies, functional traits, and responses to environmental variation can assist in producing a mechanical based predictive framework for ecologists to understand the behavior of invasive species in space and time (Huxman et al., 2013). B. tournefortii has been managed by prevention (Trader et al., 2006) and by physical and chemical control (Rice, 1992), but by little to no biological control (Sanders & Minnich, 2000). Bangle et al. (2008) noted that it displays patterns of boom-or-bust years typical of annual plant populations, demonstrating the potential existence of a substantial seed bank. When a substantial seed bank exists, seeds may cycle through different stages of dormancy, depending on environmental conditions. B. tournefortii produces numerous seeds which buried in the soil and stay viable for several years (Abd ElGawad, 2014). According to Al-Hassan (2006), 458 species were present in the northern sector of the Kingdom of Saudi Arabia, in communities similar to those here described. In north Wadi Arar area, Osman et al. (2014) recorded 196 species. Gomaa (2012) observed a total of 71 species belonging to 22 families and 61 genera in Al-Jouf provenance. These results were conforming to those by Pielou (1975) and Magurran (1988), where the taxonomic diversity is higher in an area in which the species were divided between many genera. The available vegetation data about northern region do not represent an appreciable contribution to the flora of Saudi Arabia with regard to other parts of the country (Al-Turki & Al-Qlayan, 2003). Knowledge on the ecology of this weed would help in implementing effective weed control programs and help in designing suitable weed management programs (Mahajan et al., 2018). The aim of this study was to identify the main weed communities in Al-Jouf in northern Saudi Arabia and to characterize the associated flora and species diversity, analysing vegetation and habitat conditions. MaterIals and Methods