Phosphorus Forms and Its Spatiotemporal Distribution Characteristics in Soil of Water-level-fluctuating Zone and Upper Margin of Xiangxi Bay

By using modified classification method of Hedley, the dynamic of phosphorus(P) forms at different depths of water-level-fluctuating zone and upper margin soil of Xiangxi River was monitored. The spatial and temporal dynamic characteristics of P forms of soil were discussed. Total phosphorus(TP) content of upper margin soil ranged from 0.290 to0.889 g/kg, with the trend of TP content as spring(0.676 g/kg) summer(0.595 g/kg) autumn(0.530 g/kg) winter(0.436g/kg), and there was a significant difference between spring and summer(P0.05). Apart from the residual phosphorus(ResP), other P forms had released in summer. TP content(0.543 g/kg) and available phosphorus(49.4%) in the topsoil were significantly higher than that in subsoil(0.492 g/kg; 42.3%). TP content of upper margin(0.636 g/kg) was slightly higher than that of water-level-fluctuating zone(0.567 g/kg). The lowest TP content of water-level fluctuating zone(0.354~0.807 g/kg)and upper margin soil(0.290~0.889 g/kg) were found both in WGS, other TP content distribution along the River was not obvious. P forms of soil along the River showed the similar trends with TP, and the spatial heterogeneity was significant. The studies of the spatial and temporal variation characteristics of P of the River would provide reference for governing water eutrophication of the River in the Three Gorges Reservoir.