Effects of phosphorus application on soil phosphorus forms and phoD-harboring microbial communities in an alpine grassland on the Qinghai-Tibetan Plateau

Abstract

Phosphorus (P) application to terrestrial ecosystems affects not only aboveground plants but also soil P forms and phosphatase-associated microbes. The phoD gene is widespread in soil and plays an important role in P transformation. However, it is still unclear how phoD-harboring microbial communities respond to different P application rates, and the relationships between soil properties and phoD-harboring microbial community need to be better understood. In this study, the impacts of seven P application rates [0 (P0), 10 (P10), 20 (P20), 30 (P30), 40 (P40), 50 (P50), and 60 (P60) g⋅m–2⋅a–1] on the soil physicochemical properties, P forms, and phoD-harboring microbial communities were assessed. As the results, inorganic P (i.e., Resin-Pi, NaHCO3-Pi, NaOH-Pi, and HCl-Pi) and Bio-P increased firstly and then decreased with increasing P application rate, with the highest values in the P30 treatment. Soil phoD-harboring microbial community structures in low-P (P0∼P30) treatments were significantly different from that in high-P (P40∼P60) treatments. Soil phoD-harboring microbial Shannon and Simpson diversity increased firstly and then decreased with increasing P application rate, and there was a tipping point at the P application rate of 30 g⋅m–2⋅a–1. The Mantel test and structural equation modeling (SEM) revealed that Bio-P, TC (total carbon), Fe, NaOH-organic P (NaOH-Po), and soil pH were strongly related to the soil phoD-harboring microbial community structure. In conclusion, this study demonstrated that P application affected soil P forms and phoD-harboring microbes in an alpine grassland on the Qinghai-Tibetan Plateau, and there was a P application threshold for optimistic growth of phoD-harboring microbes in an alpine grassland on the Qinghai-Tibetan Plateau.