藻类结皮自然恢复后抗风蚀特性研究

Characteristics of Natural Restored Microbiotic Crusts against Soil Erosion

从风沙物理学的角度出发，通过风洞实验研究藻类结皮对起动风速、摩阻风速、空气动力学粗糙度等的影响，探讨未破坏藻类结皮和一定程度破坏后自然恢复藻类结皮抗土壤风蚀特性。实验结果表明：无论是完好结皮还是自然恢复后的结皮，都可以提高结皮的起动风速、摩阻风速和空气动力学粗糙度长度。结皮的起动风速大于17m·s^-1，摩阻风速在0．62～1．21m·s^-1之间，空气动力学粗糙度长度在0．03～0．13cm之间。同时给出了摩阻风速和风速之间以及空气动力学粗糙度长度和摩阻风速之间的经验公式。

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·s^-1 , which is larger than that of shifting sand（ 11.08 m·s^-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·s^-1. The empirical formulas about relationships between threshold velocity and wind velocity as well as aerodynamic roughness length have been got from experiments.