Plant and Microbial Carbon Are Important Drivers of Free‐Living Nitrogen Fixation in Tropical Forest Soils: A New Discovery of Carbon‐Driven Nitrogen Input
Meichen Xu, Linjie Fan, Andi Li, Qiyan Liu, Guangcan Yu, Senhao Wang, Baixin Zhang, Qing Ye, Jiangming Mo, Mianhai Zheng
Abstract
Abstract Nitrogen (N) availability limits plant growth and soil carbon (C) sequestration in N‐limited ecosystems, however, plant and soil C feedback on the free‐living nitrogen fixation (FLNF) process is poorly understood. Moreover, whether this feedback is influenced by initial N availability in leguminous and non‐leguminous forest soils has not been clarified. Here, we found that the addition of plant‐ and microbial‐derived C significantly enhanced soil nitrogenase activity (13∼28%) and that microbial‐derived C had a more positive impact. These positive effects were attributed to the direct C‐energy supply (0.49∼0.84) rather than variations in soil microbial activity (−0.01∼0.21) and substrate resources (−0.45∼0.27). Long‐term N addition did not inhibit FLNF. C addition promoted FLNF in soils of the two forests, but the response rate was higher in the leguminous forest soils. Our study reveals that increased soil C availability can drive FLNF in tropical forests, enhancing our understanding of the soil C‐N coupling mechanism.