Hydrological influence on diversity and distribution of weedy grass species in the Hadejia-Nguru Wetland, Nigeria.

Wetlands play a crucial role in supporting biodiversity, particularly in semi-arid regions like the Sahel, where they provide vital ecosystem services. This study investigates the taxonomic diversity and distribution of grasses (Poaceae) within the Hadejia-Nguru Wetland, a Ramsar site in northeastern Nigeria. Field surveys were conducted from October 2023 to December 2024 across 12 stratified sites in both flooded and irrigated habitats. Species diversity was analyzed using the Shannon-Wiener diversity index, Simpson’s dominance index and Pielou’s evenness index, while species composition was examined through Detrended Correspondence Analysis (DCA). A total of 46 grass species belonging to 25 genera and four subfamilies were recorded, with Panicoideae emerging as the dominant subfamily. Flooded habitats exhibited a higher Shannon-Wiener index (H′ = 3.52) and lower Simpson’s dominance index (D = 0.036), indicating greater species evenness compared to irrigated fields (H′ = 3.07, D = 0.059). DCA results revealed distinct differences in species composition between habitat types, with hydrophytic species such as Echinochloa stagnina (Retz.) P. Beauv. and Oryza barthii A. Chev. & Roehr. dominating flooded areas. These findings emphasize the influence of hydrological conditions on species distribution and underscore the need for targeted conservation strategies that support both biodiversity and sustainable land use in wetland agroecosystems.