Subtropical EM- surmmcpass AM-dominated forests in increasing soil inorganic nitrogen availability: evidence from a controlled field experiment

Although the impacts of tree mycorrhizal type on soil nitrogen (N) cycling have been extensively studied in temperate forests, our knowledge from subtropical forests remains limited. We investigated soil N availability, specific N-acquisition enzyme activities (specific Nacq) and their relationships in 2-year old forests with arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) trees planting, for two seasons. Results showed that soil inorganic N (NH₄⁺-N and NO₃^–-N) and specific Nacq were significantly higher in EM than in AM forests in the summer. There was a significant negative correlation between soil specific Nacq and NO₃^–-N content, indicating that increased N availability significantly inhibited specific Nacq. This study improves our understanding of soil N cycling by revealing the relationship between soil specific Nacq and inorganic N dynamics in subtropical AM- and EM-dominated forests.