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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.

The SiO/C composite materials were prepared via a solution route and subsequent thermal treatment. The effects of carbon source on the particle morphology of composite, the graphitization degree of carbon component and the electrochemical performance of the prepared SiO/C composites were investigated by scanning electron microscopy (SEM), Raman spectrometer and electrochemical charge/discharge tests. The results reveal that the SiO/C composite synthesized with the epoxy resin as carbon source exhibits the higher graphitic degree and higher reversible specific capacity (~690 mAhg-1) and excellent cycling stability.

Spatial distribution characteristics of available phosphorus (AP) and total phosphorus (TP) in wetland soils withPhragmites australis,Suaeda salsaandTamarix chinnensiswere investigated and their influencing factors was also indentified using principal correspondence analysis for ordination in the Yellow River Delta of China. Our results showed that TP and AP contents in both sites withPhragmites australisandSuaeda salsa, and the horizontal distributions of AP content in three sites exhibited similar distribution characteristics to that of AP:TP ratios. Additionally, soil properties such as soil moisture, salinity, total nitrogen, total carbon and pH values were the important influencing factors of higher spatial variability of AP and TP.

Spatial variability of soil nitrogen and phosphorus in the Yellow River Delta was investigated using geostatistical method. Our results showed moderate variation in TN and TP and high variations in NH4+-N and AP. The best semi-variogram model for each nutrient was identified. The model parameters suggested that the structure variance dominated the total variance of TN, TP and NH4+-N, while the spatial variability of AP was relatively random. The spatial variation scales of soil nitrogen and phosphorus are similar.