Priming effect and soil carbon balance responses to plant residues from diverse tree species and tissues

Plant residues serve as a critical source of soil organic matter and can modulate the mineralization of soil organic carbon via the priming effect. This process is crucial for the storage capacity and stability of organic carbon in terrestrial soils. Most studies have investigated the priming effect of plant residues, but still do not clearly understand whether priming effects alter the soil carbon balance. Therefore, this study employed stable isotope tracing technology and carried out a 200-day microcosm simulation experiment to explore the impacts of six types of plant residues with different qualities on soil priming effects and carbon balance. The results showed that only stems of the Acer truncatum showed a negative priming effect (-75.70 mg CO 2 kg −1 soil); other plant residues all triggered positive priming effects (50.71–141.27 mg CO 2 kg −1 soil). While the Pinus sylvestris root triggered a net soil carbon output of 6.58 mg C kg⁻¹ , other plant residues all resulted in a net carbon input (34.11–156.04 mg C kg −1 ). The priming intensity was significantly positively correlated with soil fungal biomass, cellulose concentration, and was significantly negatively correlated with plant lignin content ( p < 0.05). Overall, our findings indicate that the decomposition of plant residues disrupts the balance of microbial available nutrients, which serves as a key determinant of the priming effect. Longer decomposition times of plant residues tended to shift the soil carbon balance toward net input. Our study demonstrates that plant residues generally promote soil carbon sequestration. This finding provides a scientific basis for future assessment of how exogenous organic matter affects carbon sequestration.