Microscopic examination of microbiotic soil crust shows that the profiles of soil with a dense cyanobacterial cover had two different layers: a surface thin layer composed of aeolian-born materials and an organic layer formed by filamentous cyanobacteria associated with sand particles. The results indicate that microbiotic cover is an important determinant of sand fixation in the Gurbantunggut Desert, northern part of Xinjiang, Northwestern China. Microscopic examination of microbiotic crusts in this study revealed an intricate network of filamentous cyanobacteria and exopolysaccharides, which binds and entraps sand grains and conglutinate fine particles with each other. Resistance to wind erosion paralleled the different disturbance levels on microbiotic soil crust. Sandy soil surface disturbances resulted in greatly decreased soil resistance to wind erosion. Maximum wind tunnel velocity in this test (25 m s- 1) did not lead to any wind erosion on the surface of undisturbed microbiotic soil crust, i.e. 100% covered by microbiotic soil crust. As for different disturbance levels, the highest threshold friction velocity was seen in the sand surface with 10% disturbance of microbiotic crust. The surface microbiotic soil crusts have great effects on wind erosion rates. Wind erosion rates for sandy soil with 0% crust cover was about 46, 21, 17 times the soil with 90% crust cover at wind velocities of 18, 22, 25 m s- 1, respectively. This study confirms that the planners and managers of nature reserves in this area should understand the important ecological roles of microbiotic crust in desert ecosystems. The reduction of trampling on the soil will eventually result in the re-establishment of biological crusts and their associated organisms, and ultimately lead to lower levels of wind erosion. Additionally, strategies should be developed to manage livestock and oil exploration in order to avoid concentrated zones of impact. © 2005 Elsevier B.V. All rights reserved.
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