Characteristics of Natural Restored Microbiotic Crusts against Soil Erosion
藻类结皮自然恢复后抗风蚀特性研究

Samples of microbiotic crusts were collected from the north part of Zhongwei-Gantang section of Baotou-Lanzhou railway,which lies in the southeast fringe of the Tengger Desert.In the colleted 8 crust samplers,there are 4 levels of disturbance,i.e.no disturbance(fine crusts),light disturbance(disturbance 10% and 20%,which is the ratio of disturbance area to total area),moderate disturbance(disturbance 40%) and severe disturbance(disturbance 80%),they were applied to simulate the effect of microbiotic crusts against wind erosion.Wind tunnel experiments were carried out to measure the critical starting velocity,threshold velocity,aerodynamic roughness length and wind profile of different disturbed and undisturbed crusts.The results indicated that the critical starting velocity of microbiotic crust is about 19 m\5s-1,which is larger than that of shifting sand(11.08 m\5s-1);the aerodynamic roughness length is between 0.03 and 0.13 cm,larger than that of shifting sand at least 40 times.When the disturbance level is 40%,the roughness reaches the maximum,which is 0.13 cm;the threshold velocity is between 0.15 and 1.21 m\5s-1.The empirical formulas about relationships between threshold velocity and wind velocity as well as aerodynamic roughness length have been got from experiments.