Studies on Correlations Among the Precipitation and Variation of Soil Water and Salt Under Robinia pseudoacacia Plantation in Coastal Saline-Alkali Area

The annual variations of soil water and salt content at different soil layers in a 33a old Robinia pseudoacacia pure plantation in the coastal salinealkali area were measured, and meanwhile the correlation between the annual precipitation and the annual variations of soil water and salt content was analyzed. The results showed that the synchronized salt content in the surface soil was the lowest, the salt content increased with the increment of soil depth. The synchronized water content at the top soil layer in the rainy season was the highest, it was reduced with the increment of soil depth. The water content at the top soil layer was reduced along with the increase of evaporation and finally lower than that of the deeper layer soil. The annual precipitation in the studied area was concentrated in the summer, which accounted for 66% of the total. The soil water content was significantly positively correlated to rainfall. The salt content in the soil was significantly negatively correlated to the rainfall. Whereas there was a negative correlation between water content and salt content at different layers of the soil. There were significant correlations among the water and salt contents at different soil layers. There was significant difference in water content between the 0-20cm and 60-80cm soil layers in March (P=00341<005), but there was no significant difference in salt content between different soil layers (P=01252>005).