Increasing phosphorus availability reduces priming effect by facilitating microbial carbon use efficiency in a subtropical forest soil

Abstract

The mechanisms by which phosphorus (P) availability regulates the priming effect (PE) induced by the addition of leaf litter with different qualities remain unclear. Here, soil samples from a subtropical Pinus massoniana forest were added with/without P and/or high- and low-quality ¹³C-labeled leaf litter. The samples were then incubated in the laboratory for 75 days to assess the PE, microbial community composition, enzyme activity, and microbial carbon use efficiency (CUE). The results showed that litter addition led to a positive PE. High-quality litter inputs stimulated microbial activity but reduced microbial CUE, resulting in a higher PE intensity. By contrast, the PE exhibited a decrease with P addition. Such finding indicates that strategies for obtaining P, such as microbial decomposition of soil organic matter, may be reduced. The random forest analysis revealed that microbial CUE is the dominant factor regulating PE, accounting for 62% of the variation in PE, and it exhibited a negative effect on PE. Collectively, our findings emphasize that P availability regulates PE by decreasing microbial decomposition and increasing CUE, highlighting its essential role in carbon-climate feedbacks.