Elucidating the distribution patterns and driving mechanisms of herbaceous plant diversity provides a critical scientific basis for developing ecological protection strategies. This study conducted a systematic survey of herbaceous plant communities in Yongdeng County， Lanzhou City， using a grid sampling method. We investigated four distinct habitat types-temperate steppe， temperate desert steppe， alpine meadow， and cultivated grassland-to explore the effects of topographic and soil factors on species diversity. The results indicated that： （1） A total of 356 wild herbaceous species belonging to 197 genera and 53 families were recorded. Poaceae， Asteraceae， and Fabaceae were the 3 dominant families， accounting for 38% of the total species richness. （2） The effects of topographic factors on diversity were habitat-specific. The trends of alpha-diversity indices along the elevational gradient differed significantly among grassland types， with the temperate steppe showing the most sensitive response. Species richness exhibited a significant unimodal non-linear response to slope gradient and aspect； notably， species richness peaked on shady slopes and gentle slopes due to favorable hydrothermal conditions. （3） Soil nutrients were identified as key drivers of diversity variation. Species richness was positively correlated with soil total carbon， but it showed significant negative correlations with soil total nitrogen and total phosphorus （P<0.05）. （4） Multivariate analysis further revealed that species richness was primarily driven by soil carbon content （P<0.01）. The Simpson index was significantly correlated with soil phosphorus content （P<0.01）， while the Shannon-Wiener index showed a significant co-variation with the evenness index （P<0.05）.

Herbaceous plant diversity  /  Grassland types  /  Environmental drivers  /  Topography  /  Soil nutrients  /  Yongdeng County