Weed community structure and similarity across jackfruit) orchards in Vinh Long Province, Mekong Delta, Vietnam

Abstract Understanding weed community structure is essential for designing sustainable integrated weed management (IWM) strategies in perennial fruit systems. This study aimed to characterize the floristic composition, abundance, and spatial structure of weed communities in jackfruit ( Artocarpus heterophyllus Lam.) orchards across Vinh Long province, Vietnam. Field surveys were conducted during the main rainy season of 2023 using systematic quadrat sampling across multiple agroecological zones. A total of 35 weed species in 18 families were recorded, with Poaceae being the most dominant family (10 species, 28.6%), followed by Asteraceae and Cyperaceae (4 species each, 11.4%). Quantitative metrics including density, mean field density (MFD), relative MFD, cover, and multiplied dominance ratio (MDR) identified a consistent group of dominant species: Ludwigia octovalvis (Jacq.) P.H.Raven, Ageratum conyzoides L., and Axonopus compressus (Sw.) P.Beauv., while sedges such as Fimbristylis quinquangularis (Vahl) Kunth also contributed significantly. Hygrophilous species such as Peperomia pellucida (L.) Kunth, Centella asiatica (L.) Urb., and Pouzolzia zeylanica (L.) Benn. showed high mean occurrence field density (MOFD), whereas A. conyzoides and L. octovalvis dominated relative MFD, indicating adaptation to high-light environments. Diversity indices (Margalef’s richness, Shannon’s H′, Pielou’s evenness, and Simpson’s dominance) differed modestly among agroecological regions. Ordination analysis grouped species along a gradient primarily associated with density and cover. Similarity indices (Jaccard and Sørensen) were uniformly high (mostly >0.75), suggesting strong species overlap between regions. Notably, community composition shifted with orchard age, with older orchards exhibiting less species mixing. Weedy rice ( Oryza sativa f. spontanea ) was detected but was relatively infrequent. These findings provide a quantitative baseline for designing integrated weed management strategies in perennial fruit systems. Specifically, the results support a transition away from routine herbicide use toward ecologically based practices such as mowing before flowering and selective suppression of high-importance weeds, tailored by orchard age and site conditions.