Abstract: Abstract Aims Litter quality plays an important role in regulating the magnitude and direction of soil priming effect. However, it remains unclear how the inputs of litter with different carbon to nitrogen ratios (C:N) affect soil priming effect. Methods Cunninghamia lanceolata seedlings were 13C-labeled. To obtain low and high C:N of C. lanceolata leaves, stems, and roots, one half of the C. lanceolata seedlings were fertilized and another half were unfertilized. The priming effect is quantified by the difference in CO2 emissions from native soil organic carbon (SOC) between soil amended with and without litter. Moreover, this research investigated the impacts of the input of low C:N and high C:N C. lanceolata leaves, stems, and roots on the soil priming effect and to clarify the mechanism via measuring soil microbial biomass, enzyme activities, and soil available nitrogen content. Important findings After 180 days of incubation, the input of C. lanceolata leaves induced a positive priming effect at the early stage of incubation. However, over the entire incubation period (180 days), it had no significant effect on SOC mineralization. The input of low C:N of C. lanceolata roots decreased SOC mineralization by 10.1% and induced a negative priming effect. However, the addition of C. lanceolata roots high C:N of as well as the C. lanceolata stems had no significant effect on SOC mineralization. Different C:N (high vs. low) of the same organ of C. lanceolata had no significant effect on soil priming effect. The additions of litter with different C:N did not significantly affect soil microbial biomass carbon and related C metabolic enzyme activities. The structural equation model showed that priming effect was mainly affected by 13C-microbial biomass carbon (MBC), soil available nitrogen, microbial biomass nitrogen (MBN) and β-glucosidase. These factors could explain 30%of the variation of priming effect. Moreover all factors (except for 13C-MBC) were negatively correlated with soil priming effect.

Key words: priming effect, litter quality, carbon to nitrogen ratio, soil organic carbon mineralization, Cunninghamia lanceolata