National Natural Science Foundation of China

Background and aims Ammonium nitrogen and nitrate nitrogen that can be absorbed and utilized by plants are heterogeneously distribute in nature soil, which will affect the plant growth and bacterial communities. This study aims to investigate the effects of single and mixed nitrogen (N) on bacterial communities in rhizosphere and root surface of Cunninghamia lanceolata (CR, CRS) and Schima superba (SR, SRS) seedlings.Methods Three N ratios Ammonium nitrogen: nitrate nitrogen = 10:0, 5:5(control, CK), 0:10 were set to grow seedlings in pot culture with sand. The bacteria in the rhizosphere and root surface of the tree species were determined by High-throughput sequencing (16S rDNA), and bacterial numbers and growth indicators were fitted linearly.Results Compared with the CK, the 0:10 increased the bacterial numbers, richness and diversity in CR, while the 10:0 and 0:10 were both decreased them in CRS, SR and SRS, which was more similar between the 0:10 and CK. Overall, the bacterial numbers and richness were: CR > SR > CRS > SRS, but no obvious rule in diversity. The dominant bacterial phyla in CR and CRS were mainly Proteobacteria and Bacteroidota, while in SR and SRS were mainly Proteobacteria and Acidobacteriota. Except for the root biomass of S. superba, the linear relationship of other indicators in the rhizosphere were greater than root surface.Conclusion Mixed N was more conducive to bacterial community proliferation, and there were significant differences between the two tree species and the bacterial communities at different rhizosphere sites.