Floristic Composition of Weed Vegetation in Citrus Orchards in Aljouf Region, Kingdom of Saudi Arabia

Abstract

The present work aimed to study the floristic composition and species diversity of weed assemblages in citrus orchards in Aljouf region, Kingdom of Saudi Arabia. Floristic lists were prepared and species coverage values were determined in 20 stands, using ten quadrats (1 × 1 m) per stand. In total, 33 plant species belonging to 15 families and 30 genera were identified. The largest families were Asteraceae and Poaceae (5 species for each), followed by Fabaceae (4 species), Chenopodiaceae and Polygonaceae (3 species for each). Therophytes represented the dominant life form (66.7% of the total flora), followed by geophytes (12.1%), chamaephytes, hemicryptophytes (9.1% for each) and phanerophytes (3%). The application of TWINSPAN (Two Way Indicator Species Analysis) classified the weed vegetation into four groups dominated by Plantago lagopus, Cynodon dactylon, Imperata cylindrica and Convolvulus arvensis. The species richness for the vegetation group dominated by Plantago lagopus was significantly higher (15.8 species/stand) than for the other vegetation groups. Shannon index and evenness did not show significant differences among the different vegetation groups. The species richness of citrus orchards was relatively high which could be related to the environmental heterogeneity due to different light conditions in citrus orchards.