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乌兰布和沙漠沿黄段冻结对沙丘坡面风积沙运移特征影响

Effects of Freezing on Migration Charactersitics of Aeolian Sand in Sand Dune Along Bank of Yellow River in Ulan Buh Desert

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【Author in Chinese】 赵纳祺

【Supervisor】 汪季李锦荣

【Author's Information】 内蒙古农业大学, 水土保持与荒漠化防治, 2018, 硕士

【Abstract in Chinese】 选择乌兰布和沙漠黄河沿岸刘拐沙头典型沙丘为研究对象,通过野外定点观测和室内分析相结合的方法,研究了乌兰布和沙漠典型沙丘坡面累计输沙量、风沙流结构、坡面风蚀厚度及沙盘模拟风蚀率等内容,对比分析风沙运移规律在冻结期和非冻结期差异性。该研究能够对黄河沿岸风沙入黄量的准确估算提供科学依据,为当地防沙治沙工程完善提供依据。研究结果表明:(1)乌兰布和沙漠冬季最大冻土层深度范围55.0-60.0 cm,地中土壤温度可达到零下最深处为60 cm,地中70 cm和90 cm土壤温度和水分基本不受外界干扰,随着土壤深度的增加,土壤温度达到零下越晚、重回零上越早,进而在零下维持的时间越短;在冻结过程中,土壤水分由未冻层向冻结层迁移,即水分向上迁移;离地50 cm和150 cm处空气温度、湿度变化规律基本一致,但冻结期空气湿度平均值大于非冻结期空气湿度平均值。(2)冻结期累计输沙量较非冻结期累计输沙量坡顶减少6.34%-24.46%,坡中减少9.5%-26.71%,坡底减少15.44%-25.48%;同风速条件下,坡顶、坡中的下层和上层输沙率均为非冻结期>冻结期,中层输沙率冻结期>非冻结期;将输沙量与高度进行拟合后,冻结期多遵循指数函数(y=aebx)和幂函数关系(y=axb),而非冻结期多遵循指数函数(y=aebx)关系,少数情况下出现对数函数分布(y=aln(x)+b)。(3)冻结期坡底、坡中、坡顶均呈风蚀状态,且坡中风蚀程度最为严重;非冻结期坡底、坡中呈风蚀状态,而坡顶呈沙埋状态。(4)非冻结期,初始含水率2%的沙盘土壤风蚀率大于CK,初始含水率4%的沙盘土壤风蚀率较CK降低了0.46%-23.72%,初始含水率6%的沙盘土壤风蚀率较CK降低了61.78%-91.27%;冻结期,初始含水率2%的沙盘土壤风蚀率较CK降低了20.31%-52.52%,初始含水率4%的沙盘土壤风蚀率较CK降低了23.75%-81.39%,初始含水率6%的沙盘土壤风蚀率较CK降低了14.81%-81.19%;同风速条件下,与非冻结相比,初始含水率2%、4%沙盘土壤冻结后可减少沙盘风蚀率70.96%-87.03%,CK减少30.24%-70.71%,初始含水率6%的沙盘风蚀率减少12.14%。

【Abstract】 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%.

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