Extraradical hyphae exhibit more plastic nutrient‐acquisition strategies than roots under nitrogen enrichment in ectomycorrhiza‐dominated forests

Abstract Ectomycorrhizal (ECM) functional traits related to nutrient acquisition are impacted by nitrogen (N) deposition. However, less is known about whether these nutrient‐acquisition traits associated with roots and hyphae differentially respond to increased N deposition in ECM‐dominated forests with different initial N status. We conducted a chronic N addition experiment (25 kg N ha −1 year −1 ) in two ECM‐dominated forests with contrasting initial N status, that is, a Pinus armandii forest (with relatively low N availability) and a Picea asperata forest (with relatively high N availability), to assess nutrient‐mining and nutrient‐foraging strategies associated with roots and hyphae under N addition. We show that nutrient‐acquisition strategies of roots and hyphae differently respond to increased N addition. Root nutrient‐acquisition strategies showed a consistent response to N addition, regardless of initial forest nutrient status, shifting from organic N mining toward inorganic N foraging. In contrast, the hyphal nutrient‐acquisition strategy showed diverse responses to N addition depending on initial forest N status. In the Pinus armandii forest, trees increased belowground carbon (C) allocation to ECM fungi thus enhancing hyphal N‐mining capacity under increased N availability. By comparison, in the Picea asperata forest, ECM fungi enhanced both capacities of P foraging and P mining in response to N‐induced P limitation. In conclusion, our results demonstrate that ECM fungal hyphae exhibit greater plasticity in nutrient‐mining and nutrient‐foraging strategies than roots do in response to changes of nutrient status induced by N deposition. This study highlights the importance of ECM associations in tree acclimation and forest function stability under changing environments.