摘要
玛曲草原是著名的高原牧场,也是黄河上游重要的水源涵养地,通过卫星影像分析和实地观测数据,对其风沙地貌进行分类,以期为沙化草地治理提供参考。玛曲沙化草地的风沙地貌可分为4级17类。横向沙丘(新月形沙丘)主要分布在河岸和黄河的一级或二级阶地上,单个的新月形沙丘最大高度可达12 m,64%的新月形沙丘迎风坡走向与当地起沙风向一致。分布在古河道或古三角洲的流动和半流动纵向沙丘(沙垄)高度小于3 m,51%的沙垄走向与当地起沙风向相同。低山上的沙垄和沙片出现在山顶或其阳坡,地形过渡带形成风蚀坎。风蚀洼地与固定和半固定沙地伴生,60%左右的风蚀洼地横切面为不规则椭圆和马蹄形;其深度与长轴呈正比例函数关系。古(现代)沉积物提供了丰富的沙源,大风、冻融、土层的岩性差异、脆弱的植被、人类过渡干扰和微地形促成了玛曲草地沙化和风沙地貌分异。通过对风沙地貌分类、分析,提出了以保护草皮免受破坏,为防止玛曲草地沙化的主要措施。
The Marqu with rangeland area of 8.57×107 hm2 is hailed as the first pasture of Asia.At present,the desertificated area is 0.6% of the total area of the Marqu county whith 7 136.77 hm2 of desertificated land and 3 600 hm2 of potential rangeland sandification,and has been expanding by the effect of climate change and people action.A field measure on eolian lanform will give reference to control the desertificated grassland of Marqu.In July and August of 2008,we investigated the grassland of Marqu county referrenced satellite image,and measured the eolian lanform,such as sand dunes and sandy blowouts and so on at plains and hills by GPS,compass and other instruments.The surveyed result shown as follows: the eolian lanform of Marqu might be classified in 17 classes or 4 grades by reference standards of dynamic factors,dynamic bed surfaces,activity and shape of sand dunes.The desertificated grassland centralized at terrace of Yellow River and middle or lower reaches of streams in Marqu,and there were also sandy grasslands on many of hills at Marqu.The sand dune was higher at first and second terraces of Yellow River than that of dunes at others places,and the highest sand dune was 12 m with the SSE direction of 64% of barchan dunes.Another place where many moving sand dunes distributed was the remaining delta including Yellow River and its branches.Most of shift and semi-shift sandy ridges with 3 m height hold the remaining delta,and prevail direction of sand ridges was NNW of 51 % of line ridge.At top of hill or adret,the line ridge and sand sheet usually was found,and distributed at the transition of landforms.The sandy grassland blowout and eolian bank were fund at fixed and semi-fixed sandy land and the transition zone between sandy land and grassland.The shapes of sandy blowout were roundness,oval,arch and horseshoe,while 60% of sandy blowouts,which connected with fixed or semi-fixed sandy dunes,were oval and horseshoe.It was direct proportional function as Y=0.49x-0.11(R2=0.899,and Y is depth,x is macro axis of blowout) which expressed the functional relation between depth and macro axis of blowout.The eolian bank with a shape as curtain usually distributed at transition zone between two landforms,such as shoulder of slope and passageway.The sedimentation of blown-sand from ancient to present supplied rich source of sand at the terraces for desertification grassland,as well as deposit rock.It was the active role that powerful wind with direction of NNW.The immense difference of physical property between surface and under layer,friable vegetation and people action accelerated differentiation and the desertification of grassland in Marqu.It is much important that the surface of grassland was prevented to destroy for controlling desertificted-grassland,while it is difficult that vegetation is destroyed to control grassland desertification with the more and more people actions at the grassland of Marqu.It is potential hazardous that surface of grassland is opened with sand under turf,while it will be much easier to prevent the land surface is destroyed for control grassland to desertify than that of improved and controlled desertificated grassland at Marqu grassland.There are mainly two deposit sandy landform which is like the general eolian-deposit morphology,such as dune and ridge which are fashioned into by wind with rich sand at Muqu region located at Tibet Plateau with cold climate,while the vegetation and local landform are special.The eolian landform,such as sandy grassland blowout and eolian bank is affected strongly by vegetation,structure of land,local morphology and cold climate,which is a characteristic of type and distribution of eolian landform at Muqu region with grassland,hill and cold climate.
出处
《干旱区地理》
CSCD
北大核心
2012年第3期348-357,共10页
Arid Land Geography
基金
甘肃省技术研究与开发专项计划项目(0805TCYH030)
国家自然科学基金项目(31060080)资助
