The microstructure and formation of biological soil crusts in their early developmental stage |
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摘 要: | Biological soil crust is a complex organic integrity ofcyanobacteria, green algae, lichens and mosses, fungi, andother bacteria. This is a common phenomenon in desertareas all over the world. Biologically, this kind of crustdiffers a lot from physical soi…
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关 键 词: | 生物土壤结皮 显微结构 土壤黏结力 沙漠 形成条件 化学因素 物理因素 |
收稿时间: | 1 November 2004 |
The microstructure and formation of biological soil crusts in their early developmental stage |
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Authors: | Yuanming Zhang |
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Institution: | e-mail: zhang-y-m@263.net |
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Abstract: | The biological soil crust serves as one of the biological factors contributing to the sand fixation in the Gurbantunggut Desert,
the largest fixed and semi-fixed desert in China. This study was conducted to investigate the microstructure and formation
of biological soil crusts which develop as a result of occurrence of cryptogams. One year after removal of biological soil
crusts, the exposed surface could be fixed by bacteria, which make sand particles cohere by exopolysaccharides. The exopolysaccharides
were mainly composed of glucose, mannitol, arabinose and galactose. The intension of pressure for this kind of crust is 13.42±1.38
Pa. After four-year recovery of the exposed sandy surface, the biological soil crust resulting from the colonization of soil
surface by communities of filamentous cyanobacteria were mainly dominated byMicrocoleus, which occurred as a cluster of filaments surrounded by a gelatinous sheath. At this developmental stage, the main contributors
for sand fixation were changed from bacteria to filamentous cyanobacteria. Microscopic examination of this kind of crust revealed
an intricate network of filamentous cyanobacteria and extracellular polymer secretions, which binds and entraps mineral particles
and finer particles on the filament surface. These effects enhance soil cohesion and resistance to erosion. The intension
of pressure for this kind of crust is 32.53±3.08 Pa. |
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Keywords: | biological soil crust microstructure soil cohesion the Gurbantunggut Desert |
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