Habitat fragmentation reduced plant functional diversity in the agro-pastoral ecotone of Inner Mongolia

• Habitat fragmentation reduced plant functional diversity. • This study supported the Functional Diversity-Area Relationship (FDAR). • The landscape emerged as the primary influencing factor on functional diversity. Habitat fragmentation was widely recognized as a critical factor influencing biodiversity. Current research primarily focused on the taxonomic dimensions of biodiversity; however, the impact of habitat fragmentation on plant functional diversity remains less understood. Our study examined 82 remnant grassland patches in the Tabu River Basin, located in the typical agro-pastoral ecotone of northern China. We employed Generalized Linear Model (GLM) and Structural Equation Model (SEM) to explore the effects of predictive variables (landscape variables and environmental variables) on plant leaf functional traits and functional diversity within fragmented landscapes in this region. The results showed that significant correlations were observed among leaf functional traits of 158 species in the study area, suggesting the existence of a trade-off strategy, which is consistent with the leaf economic spectrum theory. Patch area, patch isolation, mean annual precipitation and slope were identified as primary influences on leaf functional traits. Furthermore, the landscape significantly influenced functional diversity, directly or indirectly through microclimate variation. Additionally, this study supported the Functional Diversity-Area Relationship (FDAR), where we found patch area had significant positive effect on FRic. Our findings suggest that protecting patches with larger areas and gentle slopes can effectively enhance plant functional diversity and growth. This conservation strategy becomes crucial when effective measures to prevent habitat loss are lacking.