Phosphorus fertilization enhances terrestrial carbon cycling in phosphorus-deficient ecosystems

Anthropogenic phosphorus (P) input into terrestrial soils have been greatly increased, with potential effects on both above- and belowground carbon (C) cycling processes. However, uncertainty about how plant-soil-microbe systems respond to P fertilization makes it difficult to predict the effects of anthropogenic P input on the terrestrial C cycling. In this study, we conducted a global meta-analysis, examining 1183 observations from 142 publications. The findings revealed that P fertilization consistently promoted C cycling variables in plant-soil-microbe systems, resulting in improvements ranging from 7.6% to 49.8% across various ecosystem types. Notably, these positive effects of P fertilization were more pronounced with higher application rates and longer experimental durations. As the background P contents increased, the functions of P fertilization in C cycling variables shifted from positive to negative. Structural equation modeling demonstrated that changes in plant inputs predominantly drove the positive impacts of P fertilization rate and experimental duration, as well as the negative impacts of background P contents on soil respiration and microbial biomass C responses to P fertilization. Our study demonstrated the coherent responses of terrestrial C cycling processes to P fertilization and highlighted the significance of P fertilization boosting C cycling processes in P-deficient ecosystems. We suggested that minimizing the application of P fertilization in P-rich environments would enhance C sequestration and reduce P-induced environmental pollution.