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A field experiment was carried out at three different water levels and four salinity levels to study the effects of water level and salinity on nutrient contents in mash soil of the Yellow River Delta, China. Contents of total nitrogen (TN) and total phosphorus (TP) in surface and subsurface soils were measured under different water and salinity levels during the study period. Results showed that TN contents gradually decreased with increasing salinities and the highest content appeared in surface soils in different sampling dates. Higher TN contents in August (361.55 mg/kg) and September (412.17 mg/kg) were observed under 0.52 and 16.7‰ salinity treatments, respectively, and 10 cm water level, and the highest value in October (504.81 mg/kg) was observed under 10.2‰ salinity treatment and 0 cm water level. TN contents showed significant differences among different water treatments. Similarly, TP content also appeared an accumulation in surface soils in each sampling date. However, significant differences of TP contents in subsurface soils were observed among three water levels. Salinity significantly influenced the changes in TN and TP contents in both soil layers under different water level treatments. Soil TN and TP contents were significantly correlated to soil organic matter. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine whether wetland degradation in the Yellow River Delta has an effect on its soil properties. Twenty soil samples collected from degraded and undegraded wetlands were analyzed using hierarchical cluster analysis and principal correspondence analysis. The statistical analyses revealed that soil samples from both degraded and undegraded wetlands could be clearly distinguished according to their properties. These soil properties such as nitrate nitrogen, ammoniac nitrogen, and pH showed significant changes after wetland degradation than before. However, degraded wetland soils did not exhibit significant changes in electric conductivity (EC) and soil organic matter (SOM). Six soil properties excluding EC and SOM were transformed to establish a simplified chemical index of soil degradation (CDI) for evaluating wetland soil quality before and after wetland degradation. Lower CDI values of undegraded wetland soils were observed than those of degraded wetland soils. The methods used in this study can be further used in larger areas to evaluate and monitor the degradation status of wetlands, and can contribute to wetland management and restoration practices. [ABSTRACT FROM AUTHOR]

Abstract: Wetland cultivation and its effects on soil properties in salt marshes in the Yellow River Delta, China were examined by using a combination of the satellite imageries and field experiments. Results showed that the conversions mainly occurred between dry lands and Phragmites australis–Suaeda salsa–Tamarix chinensis marshes (PSTMs). The total area of marsh wetland was reduced by 65.09km2 during the period from 1986 to 2005, and these conversions might be attributed to a combination of farming, oil exploration and water extraction, as well as soil salinization. Significant differences were observed in bulk density, pH, salinity and NO3 −-N between different land-use types (P <0.05). After the conversions from marsh wetlands to dry lands, bulk density, pH, salinity and NH4 +-N decreased slightly, while a significant increase in NO3 −-N, TN (total nitrogen), and AP (available phosphorus) (P <0.05) was observed. The more loss of soil nutrient storage also occurred after the maximal area conversion from PSTMs to dry lands compared to other conversions during the study period. The storages of soil organic matter, NH4 +-N and total phosphorus decreased greatly under the conversion from three types of marshes to dry lands, while those of NO3 −-N, AP and TN showed an obvious increase during the whole study period. [Copyright &y& Elsevier]