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

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 yr-1) in two ECM-dominated forests with contrasting initial N status, i.e. a Pinus armandii forest (with relatively low N availability) and a Picea asperata forest (with relatively high N availability), to assess nutrient-mining and -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..., Study sites and the N-addition manipulation
The study sites were located at Tudiling Giant Panda National Park nearby the Maoxian Ecological Station of the Chinese Academic of Sciences (31º41´N, 103º53´E) in Maoxian country, Sichuan Province, China. According to the long-term meteorological monitoring data of the station, the mean annual temperature, precipitation, and evaporation are 8.9℃, 920mm, and 796 mm, respectively. A chronic N-addition experiment was conducted in two adjacent ECM-dominated coniferous forests, a Pinus armandii forest and a Picea asperata forest, to disentangle the effects of chronic N deposition on the structure and function of these forests. These two forests were planted in the 1970s under the auspices of a local reforestation program. The soils in both forests are classified as a Cambic Umbrisol. Compared with the Pinus armandii forest, the Picea asperata forest has higher concentrations of soil organic C, total N, dissolved inorganic N (DIN, NH4++NO3-), DIN: ...,