Nitrogen stimulation of soil carbon content differs between two types of mycorrhizal‐dominated ecosystems

Increasing nitrogen (N) deposition has been suggested to favour arbuscular mycorrhizal (AM) plants over ectomycorrhizal (ECM) plants, but how mycorrhizal association mediates N impacts on soil organic carbon (SOC) remains unclear. By synthesizing 315 N addition studies globally, we investigated the effects of N addition on SOC content in ecosystems dominated by ECM and AM plants (ECM and AM ecosystems). Our results showed that SOC increased by 4.1% in ECM ecosystems, likely due to reduced ligninase activity. In AM ecosystems, SOC did not change during the first 5 years of N addition, but increased by 7.3% over long‐term N addition (≥5 years), driven by increased litter inputs and progressive soil acidification. These findings highlight that N addition enhances SOC in both ECM and AM ecosystems via distinct mechanisms and temporal dynamics, implying that the potential of soil C sequestration may differ between the two ecosystems from short‐ to long‐term N addition. Read the free Plain Language Summary for this article on the Journal blog.