Forms and vertical distributions of soil phosphorus in newly formed coastal wetlands in the <scp>Yellow River Delta</scp> estuary

Abstract

Abstract To study the forms and vertical distributions of soil phosphorus (P) in a newly formed coastal wetland in the Yellow River Delta estuary, China, two transects from the Yellow River bank to the bare beach that encompassed a variety of vegetation covers were selected for soil sampling and field monitoring. A modified sequential fractionation method was used to partition the soil P, and the related properties were measured. The soils in this newly formed estuarine coastal wetland, only covered by salt‐tolerant plant communities, are strongly alkaline (pH 8.4–9.2) with high soil salinity (mean, 6.23‰). The content of total P (Pt) ranged from 548.3 to 728.5 mg kg −1 in these soils. Dil.HCl‐P i (extracted with 1 M HCl) was the highest P fraction (mean, 58.1–72.8%), whereas NaHCO 3 ‐P i was the lowest fraction (mean, 0.4–1.7%) of all the P forms. Vertical distributions showed a surface accumulation of Resin‐P. Resin‐P, NaHCO 3 ‐P i , NaOH‐P i , and Conc.HCl‐P i (extracted with 11.3 M HCl) were positively or negatively correlated with some properties. Attributed to the spatial deposition and hydrology, Dil.HCl‐P i presented a poor correlation with Ca. The results also showed some clear differences in the P forms and P availability among vegetation covers. The vegetation cover could modify the soil quality, and Suaeda heteroptera , as the pioneer plant community species, significantly enhanced the freely exchangeable P i and increased P availability, providing important ideas for salt‐soil sustainable use.