Deep soil microbial carbon use efficiency responds stronger to nitrogen deposition than top soil in tropical forests, southern China

Soil microbial carbon use efficiency (CUE), a key parameter determining soil C fate, has been associated with soil nitrogen (N) availability. However, the responses of forest soil CUE to aggregated N deposition are not clear. Moreover, it remains unclear whether responses may be mediated by soil depth. It is crucial to investigate the patterns and drivers of CUE with N deposition in forest top and deep soil. This study examined the responses of microbial CUE to short-term N addition treatments in the top (0–10 cm) and deep (60–80 cm) soils from two tropical forests in Hainan, southern China. Additionally, a meta-analysis was conducted to reveal a global pattern of forest soil microbial CUE response to N deposition. The addition of N in the two tropical forests did not change topsoil CUE, whereas deep soil CUE increased by 25.5