Soil phosphorus fractionation and its association with soil phosphate-solubilizing bacteria in a chronosequence of vegetation restoration

Abstract

Vegetation restoration greatly alters soil phosphorus (P) fractions and microbial community diversity, but the response of soil P dynamics to microbial activity, particularly to that of phosphorus-solubilizing bacteria (PSB), remains unclear. This study aimed to evaluate the effect of vegetation restoration on the content of various P fractions and by extension on the diversity of PSB. We also attempted to discover the role of PSB in promoting the availability of P in vegetation restoration chronosequence. According to the vegetation restoration sequence, soil samples were collected from bare land and forests stands of 6, 10, 34, and 80 years old. The PSB was detected by phoD gene function and the soil P fractions were determined by the Hedley sequential fractionation method as modified by Tiessen and Moir. We found that vegetation restoration effectively improved soil available P content, but there was no significant difference in soil available P content in 80-year and 34-year stands. Residual-P accounted for the largest proportion in all stages of vegetation restoration, up to 55%. With stand development, the diversity of soil PSB increased and reached its maximum in R34. The rare PSB groups greatly promoted the increase of PSB abundance. Proteobacteria was the main soil PSB expressing a large amount of acid phosphatase in the whole vegetation restoration sequence, which played an important role in the mineralization of HCl-Po. Although the relative abundance of Ramlibacter and Lysobacter was relatively low, they also played important roles in the mineralization of Residual-P and NaHCO3-Po, respectively.