Sandy Desertification Processat Millennium Scale And Ten Years Time Scalein Tibetan Plateau,China

The desertification report claimed by the Chinese Academy of Forestry pointed out that 16.78%land in Tibet Province was in threat of being desertified.The desertification problem has become one of the main environmental issues in the plateau.As much as 1/8 territory being involved,China made a great effort to combat such problem.Figuring out how desertification in the plateau happened and developed is an important and useful guidance for the following attempt to fight desertification in the plateau.Investigation has been promoted for the modern sand-blown activity in the plateau.Meanwhile the satellite remote sensing images of 1990,2002 and 2014 have been applied as evidences of modern sand-blown activity.The climate change and human activity were also being studied.The mechanism how modern desertification developed was tried to be found by the means of combining modern sand-blown activity with climate change and human activity.Each way of how such factor affected modern sand-blown activity was explained in the paper.The climate factor which has made the maximum contribution in this progress was extracted by the method of mathematical statistics.There occur contiguous eolian sand deposits as thick as 1?3m in Middle reaches of Yarlung Zangbo River which probably reveal climate change in the past.The eolian sand profiles are all found spreading on higher terraces far away from the riverbed.We applied quartz OSL technique to dating samples from such profiles in the south of Tibetan Plateau with a result that these sediments were deposited at 13-11 ka and 3-1 ka,during which the climate was cold and arid.A large quantity of clastic materials produced by weathering of plateau surface is conveyed and gathered along basins and valleys of the Yarlung Zangbo River by the effect of wind,gravity,glacial and water flow.With cold and dry climate through 13-11ka and 3-1 ka,these materials were transported by strong wind.When the landform is wide and flat,the sand and dust deposited on the higher terrace.Modern sand-blown activity has gradually strengthened in the past 30 years by analyzing the remote sensing images.The fact was linked with increase in evaporation caused by the warming climate and human activity.The results show that the pattern how climate influences desertification process is not the same in different time scale.We owe the difference to the modern human activities in this rigion since 1990.