ObjectiveThis study aimed to reveal the characteristics of soil nitrogen (N) transformation in different clonal Chinese fir plantations in Yangkou National Forest Farm of Fujian. This study provided theoretical basis for artificial nitrogen management and improved seed breeding of different clones of Chinese fir plantations.MethodAn incubation experiment was carried out with 7 different kinds of 15-year old third-generation excellent culture materials and seedlings (Y003, Y008, Y020, Y061, Y062, Ysec and Ymix) as the research objects, and the basic physical and chemical properties, net N mineralization and nitrification rate of soil of different clones were evaluated.ResultThe results showed that the net rates of N mineralization and nitrification were significantly affected by different clonal Chinese fir plantations. Specifically, the net mineralization rate and net nitrification rate were -0.09-0.118 mg·kg^-1·d^-1 and -0.021-0.051 mg·kg^-1·d^-1, respectively. During the whole incubation period, the average net soil N mineralization rate of Y061 was 0.117 mg kg^-1 d^-1, which was significantly higher than that of other clones and followed by Ymix (0.046 mg·kg^-1·d^-1) and Y062(0.033 mg·kg^-1·d^-1). In contrast, the average net N mineralization rates of the other four clones were negative, indicating the occurrence of net N immobilization. The average net soil nitrification rate of the Y008 clone was the highest, which was 0.051 mg kg^-1 d^-1, followed by Ymix (0.003 mg·kg^-1·d^-1) and Y020 clone (0.007 mg·kg^-1·d^-1). There were no significant differences in soil pH, ammonium nitrogen, C/N and the composition of silt and sand, but there were significant differences in soil nitrate nitrogen, organic matter, total nitrogen and clay composition. The results showed that ammonium nitrogen, nitrate nitrogen, pH and total nitrogen in soil were the main factors affecting the net nitrification rate and were all positively correlated, In contrast, the average net nitrification rate of the other four clones was negative, indicating the occurrence of net immobilization of nitrate. There were no significant differences in soil pH and carbon (C)/N among different clones, but significant differences in soil particle size composition, organic matter and total N content. Soil pH and total N were positively correlated with net mineralization and net nitrification rate, while soil C/N was negatively correlated with sand content.ConclusionThe results showed that the soil N supply capacity and N retention capacity of Y061 and Y062 clones were significantly higher than those of other clones, and the risk of N loss such as leaching in Y008 clones was higher than that of other clones. Therefore, the clone species should be rationally selected to ensure the soil fertility supply in actual planting. This study provides a theoretical basis for artificial nitrogen management and improved seed breeding of different clones of Chinese fir plantations.