Nutrient enrichment weakens the positive feedback of soil organic carbon decomposition to short-term warming in subtropical forests

Aims

Nitrogen (N) and phosphorus (P) deposition, along with climate warming, are key environmental factors driving soil organic carbon (SOC) dynamics in forests. The study aimed to explore the impact of N and P enrichment on soil respiration (SR) and its temperature sensitivity (Q₁₀) under short-term warming, and to reveal the underlying microbial mechanisms.

Methods

We collected soil samples from subtropical forests with 7 years of N and P additions, and conducted an incubation experiment at 15 °C, 25 °C, and 35 °C. SR and its Q₁₀, microbial carbon use efficiency (CUE), the Q₁₀ of soil extracellular enzyme activities (EEAs) and extracellular enzyme stoichiometry (EES) were evaluated.

Results

N and P additions reduced the Q₁₀ of SR within the temperature interval of 15–25 °C (moderate environment, MoE), indicating that increased nutrient availability weakens the positive feedback of SOC decomposition to warming in the MoE. The Q₁₀ of SR in the MoE was positively correlated with the Q₁₀ of β-D-cellobiohydrolase, but not with the CUE or Q₁₀ of EES, indicating that the reaction of SOC decomposition to warming depends on changes in C cycle-related enzymes rather than microbial resource availability. N addition reduced SR at 25 °C and 35 °C, and the vector length and angle of EEAs were closely related to SR, suggesting that SR depends on microbial nutrient limitation.

Conclusion

Our study highlights the importance of the Q₁₀ of soil enzymes in predicting SOC dynamics under short-term warming. Nutrient enrichment will promote SOC sequestration under climate warming in moderate environments.