Yunpeng Qiu, Yunfeng Zhao, Bianbian Wang, Xi Xu, Tangqing He, Kangcheng Zhang, Tongshuo Bai, Zhen Li, Chenglong Ye, Christopher J. Gillespie, Xiaodong Wang, Yexin Zhao, Lijin Guo, Kaiyun Qian, Huaihai Chen, Xinxin Cao, Shuqi Wu, Liang Guo, Ripley H. Tisdale, Alex Woodley, Kevin Garcia, Weixing Zhu, Lingli Liu, Yi Wang, Yi Zhang, Shuijin Hu
Plant roots and arbuscular mycorrhizal fungi (AMF) form a ubiquitous symbiosis in terrestrial ecosystems and critically affect soil organic carbon (SOC) dynamics. However, how roots and AMF mediate the impact of reactive nitrogen (Nr) and climate warming on SOC remains unclear. Using a multi-year Nr addition and simulated warming experiment in a semi-arid grassland, we show that Nr input and warming alter SOC by reshaping plant communities and inducing multidimensional tradeoffs among fine-root traits and AMF communities. Stable isotope (13C) tracing revealed that Nr- and warming-induced changes in roots and AMF reduced C input belowground, and mineral-associated organic C and microbial necromass in soil, while stimulating organic C decomposition. Nr input also increased soil N:P ratios and shifted AMF communities toward taxa with finer extraradical hyphae, weakening SOC protection. Together, these findings highlight root-AMF interactions as critical regulators and improve predictions of long-term SOC dynamics under future climate change. N input and warming alter plant traits and mycorrhizal communities, reducing belowground C inputs and stable soil organic C while accelerating decomposition, highlighting root–mycorrhizal interactions as key regulators of soil C under global change.