The Mugetan dune field in Guinan is the largest continuous dune system in the Gonghe Basin, Qinghai-Tibet Plateau. The modern sandy desertification is derived from reactivation of fossil dunes. However, it is not yet clear how this reactivation has occurred in Guinan. By means of field investigations, interpretation of remote-sensing images, analysis of sedimentary stratigraphy, and grain-size tests, we analyze the current situation of sandy desertification in Guinan and its spatial distribution, the stratigraphic sequence and the grain size of the fossil dune sediments, and proposes a microcosmic explanation for the driving mechanism of sandy desertification. The research results show that the mobile dunes are mainly distributed on the Mugetan. The small scale geomorphology of Mugetan can be divided into two types:the plateau and sandy hills, and about 96.1% of mobile dunes is distributed on the sandy hills, and only 3.9% is distributed in the edge of the plateau. The grain size characteristics of modern mobile dunes and fossil dunes are very similar, showing obvious relationship of inheritance and transformation. Modern mobile dunes is derived from reactivation of fossil dunes. The turf and silty sand are protective layers of fossil dunes. Mechanical destruction of protective layers, leading to exposure of underlying loose sands is the key step that leads to sandy desertification in Guinan. The exposed loose sands are blown out by the wind, and created lateral recession at the bottom of the surface protective layer. When the lateral recession reached a certain depth, turf or silty sand collapsed and accumulated at the foot the scarp. The collapsed materials partly or wholly covered the exposed loose sands. Afterwards, the collapsed materials are eroded and carried away by wind, rain and gravity, and the loose sands exposed again. Alternating of wind erosion and gravity erosion, lead to blowouts expansion and connection, finally, formed mobile dunes.
[1] 冯益明,卢琦,王学全,等.青海省贵南县土地荒漠化动态变化遥感分析[J].遥感技术与应用,2008,23(6):633-638.
[2] 韩海辉,杨太保,王艺霖.近30年青海贵南县土地利用与景观格局变化[J].地理科学进展,2009,28(2):207-215.
[3] 董光荣,高尚玉,金炯,等.青海共和盆地土地沙漠化与防治途径[M].北京:科学出版社,1993.
[4] 韩永翔,奚晓霞,宋连春,等.青藏高原沙尘及其可能的气候意义[J].中国沙漠,2004,24(5):588-592.
[5] 白虎志,马振锋,董文杰,等.西藏高原沙尘暴气候特征及成因研究[J].中国沙漠,2006,26(2):249-253.
[6] 孙鸿烈,郑度,姚檀栋,等.青藏高原国家生态安全屏障保护与建设[J].地理学报,2012,67(1):3-12.
[7] 胡光印,董治宝,逯军峰,等.长江源区沙漠化及其景观格局变化研究[J].中国沙漠,2012,32(2):314-322.
[8] Yang M X,Wang S L,Yao T D,et al.Desertification and its relationship with permafrost degradation in Qinghai-Xizang (Tibet) plateau[J].Cold Regions Science and Technology,2004,39(1):47-53.
[9] 李森,董玉祥,董光荣,等.青藏高原土地沙漠化区划[J].中国沙漠,2001,21(4):420-426.
[10] Xue X,Guo J,Han B S,et al.The effect of climate warming and permafrost thaw on desertification in the Qinghai-Tibetan Plateau[J].Geomorphology,2009,108(3):182-190.
[11] Liu Y,Dong G,Li S,et al.Status,causes and combating suggestions of sandy desertification in Qinghai-Tibet Plateau[J].Chinese Geographical Science,2005,15(4):289-296.
[12] 方小敏,韩永翔,马金辉,等.青藏高原沙尘特征与高原黄土堆积——以2003-03-04拉萨沙尘天气过程为例[J].科学通报,2004,49(11):1084-1090.
[13] Han Y X,Fang X M,Zhao T L,et al.Suppression of precipitation by dust particles originated in the Tibetan Plateau[J].Atmospheric Environment,2009,43(3):568-574.
[14] 刘冰,靳鹤龄,孙忠,等.全新世共和盆地沙地时空演化及其驱动机制[J].中国沙漠,2014,34(4):982-991.
[15] 陶贞,董光荣.末次冰期以来贵南沙地土地沙漠化与气候变化的关系[J].中国沙漠,1994,14(2):42-48.
[16] 高尚玉,王贵勇,哈斯,等.末次冰期以来中国季风区西北边缘沙漠演化研究[J].第四纪研究,2001,21(1):66-71.
[17] Jin H L,Dong G R,Su Z Z,et al.Construction of the spatial patterns of desert/loess boundary belt in north China during the Holocene[J].Chinese Science Bulletin,2001,40(12):969-974.
[18] 李明治.共和盆地末次盛冰期以来的风沙活动历史与气候变化[D].兰州:兰州大学,2012:1-75.
[19] 张登山.青海共和盆地土地沙漠化影响因子的定量分析[J].中国沙漠,2000,20(1):59-62.
[20] 董光荣,高尚玉,金炯,等.青海共和盆地土地沙漠化及其防治[J].中国沙漠,1989,9(1):61-71,75.
[21] 杨世琦,高旺盛,隋鹏,等.共和盆地土地沙漠化因素定量研究[J].生态学报,2005,25(12):3181-3187.
[22] Feng Y M,Lu Q,Tokola T,et al.Assessment of grassland degradation in Guinan county,Qinghai Province,China,in the past 30 years[J].Land Degradation & Development,2009,20(1):55-68.
[23] Buynevich I,Bitinas A,Pupienis D.Reactivation of coastal dunes documented by subsurface imaging of the Great Dune Ridge,Lithuania[J].Journal of Coastal Research,2007,50:226-230.
[24] Sun J M,Ding Z L,Liu T S.Desert distributions during the glacial maximum and climatic optimum:example of China[J].Episodes-News magazine of the International Union of Geological Sciences,1998,21(1):28-31.
[25] 张春来,董光荣,邹学勇,等.青海贵南草原沙漠化影响因子的贡献率[J].中国沙漠,2005,25(4):511-518.
[26] 中国科学院地理研究所.青藏高原地图集[M].北京:科学出版社,1999:112.
[27] 罗天祥,李文华,罗辑,等.青藏高原主要植被类型生物生产量的比较研究[J].生态学报,1999,19(6):823-831.
