Abstract
The introduction of weeds into the agricultural landscape is considered a major problem that threatened the cultivated plants as weeds compete with them for water, nutrients, space and light. The information about taxonomic diversity of weeds in olive orchards in Saudi Arabia is still incomplete. The present study aims to investigate the diversity patterns and taxonomic composition of the weeds in olive orchards in four sites located in Tabuk Region in the northern part of Saudi Arabia: Juraydah, Tayma, Qulaybah, and Tabuk. A total of 46 weeds species were identified from olive orchards in the four districts. The weeds communities in the Tabuk region is dominated by Pulicaria undulata, Anisosciadium lanatum, Cynodon dactylon, Emex spinosa, and Euphorbia granulata. The highest species richness of weeds was reporte in Juraydah, followed by Qulaybah, with values of 30 and 24 taxa, respectively. However, the lowest number of weed species was reported in Tayma. The highest values of Shannon-Weiner (H') and Simpson's (1-D) indices were reported in Juraydah and Qulaybah. The diversity of species within the locations, expressed as beta diversity (beta), was also measured. The olive orchards in Qulaybah and Tayma are characterized with high diversity within sites as indicated by the high values of beta diversity of 3.231 and 3.226, respectively. The diversity measures did not show significant differences among the sites (ANOVA, P > 0.05). Based on cluster analysis, olive orchards in Qualybah showed a strong relationship in the taxonomic composition of weeds with other orchards in Juraydah and Tabuk. Further studies concerning other biological and ecological aspects of weeds in the olive orchards of Saudi Arabia are urgently needed. This will facilitate the development of effective control strategies to manage the weed communities and increase the crop yield in olive orchards of Saudi Arabia.