Short-term of nitrogen addition improves soil phosphorus availability by regulating phosphorus-cycling microbial communities in a karst forest

The widening imbalance between escalating nitrogen (N) deposition and depleting soilphosphorus (P) amplifies the urgency of investigating P cycling processes in terrestrialecosystems. However, the mechanisms by which P-cycling functional profiles drive soilP mobilization under enhanced N deposition remain to be addressed. After a three-yearN-addition experiment at varying rates in a karst forest, we determined the soil Pfractions and associated microbial communities involved in regulating P cycling inrhizosphere and bulk soils. Our results showed that N addition induced a significantincrease in the concentrations of available P while causing a parallel decrease in thoseof organic P in the two soil compartments. In addition, N treatment substantially shiftedthe composition of the P-cycling microbial community and increased the diversity andrichness of the community, indicating that N input enhances P availability, potentiallythrough the regulation of the microbial communities involved in P cycling. Moreover, wefound that the functional microbial genes responsible for P transformation differedbetween the bulk and rhizosphere soils. Specifically, in the bulk soil, P mineralizationgenes and P solubilization genes were significantly increased by N treatment. Incontrast, in the rhizosphere soil, P mineralization and P regulation genes increased inresponse to N addition. Together, these results suggest that N addition improves soil Pavailability by regulating P-cycling functional microbial communities; however, thespecific functional profiles driving P mobilization may differ between bulk andrhizosphere soils. These findings provide novel insight into the regulatory processes ofsoil P cycling in terrestrial ecosystems under global changes (e.g., N deposition) from amicrobial gene perspective.