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冰川冻土 ›› 2015, Vol. 37 ›› Issue (5): 1245-1256.doi: 10.7522/j.isnn.1000-0240.2015.0138

• 冰冻圈与全球变化 • 上一篇    下一篇

黄河源区玛多县沙漠化成因与发展过程

姚正毅, 李晓英, 董治宝   

  1. 中国科学院 寒区旱区环境与工程研究所 中国科学院沙漠化与沙漠重点实验室, 甘肃 兰州 730000
  • 收稿日期:2015-05-15 修回日期:2015-07-09 出版日期:2015-10-25 发布日期:2016-03-28
  • 作者简介:姚正毅(1969-),男,甘肃镇原人,研究员,2006年于中国科学院寒区旱区环境与工程研究所获博士学位,主要从事沙漠化与风沙工程研究.E-mail:yaozy@lzb.ac.cn.
  • 基金资助:
    国家重大科学研究计划项目(2013CB956000)资助

Causes and processes of desertification in Madoi County in the source regions of the Yellow River

YAO Zhengyi, LI Xiaoying, DONG Zhibao   

  1. Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China
  • Received:2015-05-15 Revised:2015-07-09 Online:2015-10-25 Published:2016-03-28

摘要: 通过分析黄河源区玛多县沙漠化的成因和过程,结果表明,玛多县沙漠化成因类型有三种,分别为固定沙丘/古沙丘活化、滑塌陡坎及风蚀斑块,其形成都与多年冻土退化相关.在固定沙丘或古沙丘分布区,冻土退化导致热融沉陷,形成沉陷坑,沉陷坑边缘形成拉裂缝或陡坎,使下伏松散沙露出.在斜坡上,冻土退化形成滑塌陡坎,使底层土壤从侧面暴露.在平坦的冲积平原,差异性冻胀和融沉导致草皮拉裂,形成积水坑洼,冻土退化导致土壤变干,土壤的底层暴露.下伏风成沉积物暴露后,遭受风蚀,形成侧向凹槽,致使上部土体坍塌,使更多的风成沉积物暴露,这些过程的不断重复,使风蚀坑、陡坎、风蚀斑块扩大相连,最终形成流动沙丘、风蚀劣地、戈壁等地貌.

关键词: 黄河源区, 沙漠化, 成因与发展, 沙丘活化, 风蚀坑, 滑塌陡坎, 风蚀斑块

Abstract: Under the influence of global climate change, Madoi County in the source regions of the Yellow River is facing serious ecological and environmental problems, such as desertification, wetland shrink, grassland degradation and so on. By means of field investigation, interpretation of remote-sensing images, analysis of stratigraphy and grain-size analysis, causes and processes of desertification in Madoi County are analyzed in this paper. The results show that widely distributed fossil aeolian sediments and alluvial deposits of the Yellow River and its tributaries are the material sources of the desertification in the source regions of the Yellow River. The grain size characteristics of modern mobile dunes and fossil dunes are very similar, showing obvious relationship of inheritance and transformation of them. The distribution of the modern mobile sand dunes has not exceeded the scope of the fossil aeolian deposits. Due to environment changes, fossil aeolian sediments are subsequently fixed, and dense turf forms on the surface to protect underlying loose sand. Mechanical destroy of the turf is a crucial step for modern desertification. In Madoi County, mechanical damage of turf layer is associated with permafrost degradation. Permafrost degradation is different in different landforms. On fixed/fossil dunes, subsidence pits would form on the dunes due to permafrost degradation. Tensile cracks and extending falls would form around the edge of the pits leading to expose of underlying loose sand. On the slopes, slump scarps would be created by permafrost degradation, leading to expose the underlying soil. In the flat ground such as alluvial plain, waterlogged depression would form on the surface for differential frost heave and thaw settlement. With lowering of ground water level due to permafrost degradation, the bottom layer of the soil would be exposed. The destruction of turf leads to exposure of the underlying aeolian sediments. The aeolian sediments are eroded by wind, creating lateral recession, resulting in the upper soil collapse and leading to more aeolian sediment exposed. Alternation of wind erosion and gravity erosion would expand the blowouts, slump scarps, wind erosion patches, leading to merger of them, and eventually formed mobile dunes, eroded badlands and gobi deserts.

Key words: source regions of the Yellow River, desertification, causes and processes, reactivation of fixed/fossil dunes, blowouts, slump scarps, wind erosion patches

中图分类号: 

  • P931.3