Climate and soil nutrients drive global variations in community-level root nutrient acquisition strategies

O_LITrait-based root economics space (RES) is important for understanding species-level belowground strategies. Yet, how trait coordination scales from species to community levels and its environmental drivers remain largely unknown. C_LIO_LIWe compiled global fine-root trait data from 301 natural plant communities and employed the plant trait network (PTN) method to map community-level trait covariation and explore the potential environmental drivers. C_LIO_LIThe PTN segregated root traits into two independent modules: a morphological module dominated by root diameter and specific root length, and a module dominated by root chemical traits and root tissue density, supporting the bi-dimensionality of the species-level RES. The morphological module reflects shifts in belowground strategies along a soil fertility gradient: nutrient-rich soils favor roots with greater specific root length for direct uptake, while nutrient-poor soils promote thicker roots with higher reliance on mycorrhizal fungi. Unlike the species-level coupling between root tissue density and root nitrogen concentration, however, these two traits decoupled at the community level, possibly because they were shaped by contrasting environmental factors. C_LIO_LIThis study underscores that the species-level RES is difficult to extend to the community level and provides new insights into vegetation dynamics modeling under global change. C_LI