Spatial and seasonal distributions of soil phosphorus in a short-term flooding wetland of the Yellow River Estuary, China

Soil cores were collected at a depth of 60 cm along a sampling belt perpendicular to the Yellow River of the Yellow River Estuary and were collected in both summer and fall of 2007 and the spring of 2008 to investigate spatial and seasonal dynamics of soil phosphorus in a short-term flooding wetland. Our results showed that total phosphorus (TP) levels were lowest in spring, followed by those in summer and the maximum level was in fall along the sampling belt. Lower TP levels were observed at Site 3 in summer and fall, whereas the lowest TP levels appeared at Site 1 in spring. All available phosphorus (AP) levels were higher in fall than that in spring except for Site 4. However, in summer, AP contents showed a “decreasing before increasing” tendency along the sampling belt. TP contents in profile soils exhibited a decreasing tendency from summer to next spring, whereas AP levels increased slightly from summer to fall and decreased from fall to the next spring. TP contents increased and then decreased along soil profiles in summer and spring, whereas they showed a “decreasing before increasing” tendency in fall. The mean AP levels and AP: TP ratios generally decreased along soil profiles in three sampling seasons. TP stocks ranged from 419.40 mg m− 2 to 578.45 mg m− 2 and generally exhibited an increasing tendency from Site 1 to Site 5. Approximately 50% of TP stocks accumulated in the top 20 cm soils. Higher TP stocks in the top 60 cm soils were observed in summer and fall at each of five sampling sites than in spring (p < 0.05). Correlation analysis showed that Soil TP levels were significantly correlated with soil bulk density (BD) and salinity, and AP contents were significantly correlated with soil depth and pH values. TP stocks were significantly impacted by TP, BD and pH values.