Long-term nitrogen addition increased soil microbial carbon use efficiency in subalpine forests on the eastern edge of the Qinghai–Tibet Plateau

Nitrogen (N) deposition increased forest carbon (C) sink significantly, hence exploring the microscopic mechanisms is critical to predicting future global ecosystem C cycle, especially effects of enhanced N on soil microbial use efficiency (CUE), which still unclear. We evaluated responses CUE long-term (5 years) addition in an evergreen broad-leaved and a mature coniferous by using 13C isotope tracing method. The results showed that ranged from 0.38 0.51, was smaller than obtained previous studies based same method type. In forest, had no significant changes low N-addition treatment, but it 9.23% 12.69% medium high treatments compared control. 14.64%, 21.89% 24.34% low, treatments, respectively. Moreover, C:P N:P are negatively relate CUE. Our findings indicate enhancing can increase ultimately promote sequestration, forest. imbalance stoichiometry main impact factor under addition. However, we speculate key decomposition rate litter thus available content.