Mycorrhizal type modifies the position of exudation carbon within the root economics space

The trait‑based root economics space provides a fundamental framework for understanding plant belowground adaptation to environmental change, yet it typically omits root exudation that sustains plant resource acquisition and health. Results from a ~3500 km north‑south forest transect demonstrate that arbuscular mycorrhizal (AM) trees have higher root exudation rates than ectomycorrhizal (ECM) trees, with stronger increases under warmer and wetter climates. Root exudation rate is positively related to specific root length and negatively related to root diameter for both mycorrhizal types, but is related to tissue density and nitrogen content only in AM trees. These findings suggest that root exudation may represent an alternative collaboration strategy, facilitating organic nutrient acquisition more strongly for AM species and functioning as a relatively redundant nutrient acquisition mechanism for ECM species. Moreover, mycorrhizal type modulates how exudation rates relate to the "fast-slow" strategy. Overall, our findings refine the conceptual framework of the root economics space and enhance understanding of fine‑root strategies.