Abstract

The size and stability of the soil carbon pool depend on the balance between plant litter input and soil organic carbon mineralization. As an important source of soil organic carbon, litter input plays a key role in the decomposition of soil organic carbon through the priming effect and ultimately affects soil carbon balance. Litter quality is a key factor affecting the decomposition and transformation of soil organic carbon. However, uncertainties remain regarding the effects of different-quality litters on soil mineralization and priming. In this study, we used an indoor incubation method to label China fir leaf litter and Acacia leaf litter with the isotope 13C. The effects of different-quality litters on the intensity and direction of soil priming effects were studied by adding different-quality litters to soils in different subtropical regions. The results show that, compared with China fir (Cunninghamia lanceolata) litter (low-quality, high C/N), Acacia (Acacia confusa) litter input (high-quality, low C/N) promotes soil mineralization and decomposition. By contrast, low-quality litter produces higher quantities of litter source C, which returns to the atmosphere through CO2. Different-quality litters could regulate the direction and intensity of the soil priming effect. The priming effect of the Acacia litter addition treatment was higher than that of the China fir litter addition treatment. The addition of high-quality litter promotes the generation of a positive soil priming effect. The addition of Acacia litter to different regions of soil had a positive priming effect, while the addition of China fir litter had a negative priming effect for a period of time. Furthermore, the correlation analysis results showed a significant connection between soil physical and chemical indicators and litter C/N and soil mineralization and priming effects. The random forest analysis showed that litter C/N (p < 0.01) is one of the main factors affecting the soil priming effect, indicating that litter quality has a higher relative importance to the priming effect. These findings underscore the critical role of litter quality in regulating subtropical soil carbon dynamics and providing pivotal datasets for predicting terrestrial carbon sink potential.

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