Effects of Different Flooding Frequencies on Soil Nitrogen Mineralization in Typical Floodplain Wetlands under Aerobic Conditions

Soil profiles from 0 to 80 cm depth were collected at five typical zones (including permanently flooded floodplain (B), 1-year floodplain (O), 5-year floodplain (F), 10-year floodplain (T), and 100-year floodplain (H)) which are divided by different flooding frequencies along the direction penperdicular to the river channel in different floodplain wetlands of Xianghai National Nature Reserve of China. A 14-day incubation experiment was carried out at 25°C in the dark to reveal the effects of different flooding frequencies on nitrogen mineralization rates. Our results showed that nitrogen mineralization rates showed an alternative tend of “increasing and decreasing”in the soil profiles at five sampling zones except the 1-year floodplain and permanent floodplain. The nitrogen mineralization rates were lower in permanently flooded floodplain soils compared to another four floodplain wetlands with different flooding frequencies. Additionally, nitrogen mineralization rates were significantly correlated with electrical conductivity, total soluble salt, pH values and salinity.