Biogeochemical niches modulate shoot and root biomass in <i>Potentillinae</i> across Chinese grasslands

Abstract The biogeochemical niche (BN) hypothesis posits that each species performs species‐specific functions linked to its unique elemental composition. However, the relationship between BN and plant functions—such as biomass—remains to be fully understood. In our study, we assessed the shoot and root biomass, as well as the concentrations of 10 elements in the leaves and roots of 368 individuals from 18 species within the Potentillinae across northern grasslands in China. We tested the BN hypothesis for both leaves and roots and investigated the relationships between the BN and biomass in the above‐ and below‐ground in these grasslands. Our analysis revealed that legacy (phylogenetic + species) effects explained a significant proportion of the variation in leaf and root elemental composition among species within a narrower taxonomic range, and leaf elemental composition exhibited higher phylogenetic conservatism compared to roots. Moreover, we also identified a strong connection between species B and N that estimated by leaves and roots, along with positive associations between them and the shoot and root biomass. Synthesis. Our results underscore the strong connections between the BN size and plant biomass above‐ and below‐ground. We suggest that the BN could serve as a valuable framework for linking elemental composition to ecosystem functions in grasslands.