Soil amelioration effects resulted from salt reduction by the three plantations of pure Robinia pseudoacacia

pure Populus liaoningensis

and mixed P.liaoningensis and R.pseudoacacia were studied in raised fields established by soil preparation engineering measures in saline-alkali soils along muddy seacoast of Northern China.Results showed that the three plantations were almost closed after 11 years.The reservation rates were 63%~72% and shade densities were 0.6~0.7.The height and DBH of the mixed plantation were higher than those of the two pure plantations.The desalination effects of the three planting patterns were observed within 70 cm of soil surface and soil nutrient deficiency was formed between 50 and 70 cm below soil surface.The mixed plantation increased soil organic matter content on the forest land.Within 100 cm of soil surface

the distribution rhythms of total N in soil profiles were similar to those of organic matter.The variation of the contents of total P in the three plantations was not significant.On the whole

the total amount of phosphorus was deficient and its efficiency was low.Factor analysis indicated that soil amelioration effects for the mixed plantations of P.liaoningensis and R.pseudoacacia were better than those of pure plantations

which could enhance the fertility status of saline-alkali soils along the muddy seacoast and might be applied in practice as a promising afforestation model.