Effects Of Freezing On Migration Charactersitics Of Aeolian Sand In Sand Dune Along Bank Of Yellow River In Ulan Buh Desert

This study took the Liuguai moving dune where was located in Ulan Buh Desert along bank of Yellow River as an object.Combing field observation and laboratory test,analysed which focused on the sediment transport rates,sand flow structure,the thickness of wind erosion and the rate of wind erosion in sand plates.Analysed the difference of migration process of Aeolian sand in frozen period and other period.In order to provide scientific decision-making basis for the prediction of the sediment yield of the Yellow River and theoretical foundation for the project of preventing and controlling desertification.The result showed that:(1)The depth of frozen soil could reached 55.0-60.0 cm in Ulan Buh Desert,the soil temperature could be below zero in the depth of 60 cm.The soil temperature and soil moisture undisturbed basically by the outside world in the depth of 70 cm and 90 cm.The later the temperature of the soil was below zero and the earlier returned to zero,the time in the sub-zero was shorter with the increase of soil depth.During the freezing process,soil moisture was migrated from the unfrozen layer to the frozen layer.There was no significant difference in air temperature and humidity between 50 cm and 150 cm,but the mean value of air humidity was greater than non-freezing period.(2)Compared with the non-freezing period,the cumulative sediment transport volume decreased by 6.34% to 24.46% in the top of slope in the freezing period,decreased by 9.5% to 26.71% in the middle of slope,decreased by 15.44% to 25.48% in the base of slope.Under the same wind speed,the substratum and supestratum of sediment transport rates were both non-freezing period > freezing period in the top and minddle of slope,and the middle-level of sediment transport rates was freezing period > non-freezing period.After fitting the sediment load with the height,the freezing period followed the relationship of power function and exponential function,but the non-freezing period followed the relationship of exponential function,and the distribution of logarithmic function appeared in a few cases.(3)The top of slope,middle of slope and base of slope were all wind erosion in the freezing period,and the wind erosion degree was the most serious in middle of slope.In the non-freezing period,the middle of slope and base of slope were wind erosion while top of slope was sand burial.(4)Compared with CK,the soil wind erosion rate of soil moisture of 2% was higher than CK,and soil moisture of 4% decreased by 0.46% to 23.72%,soil moisture of 6%decreased by 61.78% to 91.27% in the non-freezing period.In the freezing period,compared with CK,the soil wind erosion rate of soil moisture of 2% was decreased by20.31%-52.52%,soil moisture of 4% was decreased by 23.75%-81.39%,soil moisture of6% was decreased by 14.81%-81.19%.Under the same wind speed,compared with non-freezing period,the soil moisture of 2% and 4% of soil freezing could reduce the wind erosion rate by 70.96-87.03%,and CK decreases by 30.24% to 70.71%,and tsoil moisture of 6% decreased by 12.14%.