| The most serious environmental problem in Mongolia Plateau is land degradation and sandstorm caused by wind erosion. On account of the climatic and geographical backgrounds in Mongolia Plateau and the human being yield together effect, resulting in the wind abrasion to strengthen and the Prairie land degradation to aggravated and the soil mantle organic matter and other primary nutrient material loss and the degradation of land productivity and dust storms at the regional scale. Affecting the region ecosystem to be stable and Human economic society's to be sustainable development.The resulting dust storm is also considered as one of the most severe environmental problems in North China and East Asia.The research object is land degradation of Mongolia Plateau, It established the Tariat-Xilingol transect from northwest to southeast across the plateau region as key research region, and using the traditional methods and the modern technology .On the basis of data collection,field survey and sampling surface soil,physical and chemical properties and 137Cs activity were analyzed according to data measured practically and mainly indoor experiment.The soil particle composition and the major nutrient contents-the soil organic carbon (SOC), total N, total P and total K, were determined, and land degradation of wind erosion were discussed. On the primary of Routine analysis of soil, the soil wind erosion rates was estimated by using the revised models of 137Cs tracing technique. Then, the land degradation spatial dynamics was discussed. The provides method and technology as a reference for quantitative research of drought and semiarid region land degradation. The main research results and innovation are summarized as following: (1)The results of routine analysis:1)The wilderness and desertification area and prairie area abandoned farmland sampling points soil mantle and A layer particle, as a whole is lower than the prairie sampling point.Explains that for a long time strong wind erosion process wilderness and the desertification area as well as the prairie abandoned farmland surface layer soil were coarsened .2)The SOM and the total N content spatial distribution were lower in the middle transect sites and higher in the north and south sections. Increased with increasing annual precipitation and increassing vegetation coverage; The SOM and the total N content was mainly affected and controlled by physical factors in the Mongolia section of the study transect. In the prairie ,the SOM and the total N content of depth distributions showed the exponentially declining patterns with the increasing depths ;In Holahoi abandoned farmland distributed in the 25-cm-depth plough layer due to the annual tillage.3)Soil mantle of abandoned farmland in Holahoin is arid,because of the wind erosion ie stronger than prairie area;The wind erosion ie also stronger than prairie area in the wilderness and the desertification area; Xilinhot, Zhengxiangbai Banner The wind erosion is stronger than Baynnor.(2) The results of radionuclide aesium-137tracing:1) Through specific sampling strategy and collecting methods, a large number 137Cs with different soil types or land use in each typical area in Mongolia Plateau were gathered and analyzed. The 0-30cm 137Cs inventory in different typical soils is in order of Xilinhot>Tariot>Baynnor> Zhengxiangbaiqi>Luss>Elerjet>Sainsand. Examining the 137Cs distribution along the soil profiles, the depth of 137Cs along soil profiles is about 0-15cm in research transect. Except the cultivated land in Holaholin in which the 137Cs is distributed averagely along the soil profile, the distributions of 137Cs in other soils are all in negative exponent pattern. And in the three soil profiles of Tariot sylvosteppe (RF1), Baynnor typical grassland (RF2) and Xilinhot meadow grassland (RF3), there maintained the relatively perfect profile of origin 137Cs fallout which can be regarded as ideal sampling site of 137Cs reference.2) The annual surface soil loss ranged from 0.04 to 4.8 mm·a-1, and the wind erosion rates of the steppe sampling sites of the transect ranged from 64.58 to 7987.92 t·km-2·a-1, respectively. The wind erosion rate in Tariot, Baynnor(WE2-B1,WE2-B2,WE2-B3 ),Holahoin, Luss, Elerjet, Sainsand, Xilinhot, Zhengxiangbai Banner is estimated respectively to 172.37,169.07,103.46,64.58,7987.92,206.34,276.24,419.63,360.02,351.33 t t·km-2·a-1 averagely.The abandoned farmland in Holahoin, however, was strongly eroded by wind, with erosion rates up to 7987.92 t·km-2·a-1.3)In general, the trend of the wind erosion rates in the Mongolia section can be summarized as follows: from north to south, wind erosion increased with decreasing annual precipitation and decreasing vegetation coverage; wind erosion increased and biodiversity decreased when ecosystem structure was simplified from typical steppe, desertification steppe, steppe desert to Gobi desert. The wind erosion process was mainly affected and controlled by physical factors in the Mongolia section of the study transect. In the typical steppe zones of the north and south section of the transect, the wind erosion rates at Site Xilinhot, Site Zhengxiangbai Banner is higher than that at Site Bayannur. The results showed that intensive human activity may be responsible for the more severe wind erosion in the Inner Mongolia section.4)The wind erosion rate at each site is beyond the slight level except for Tariat and Bayannur. The ecosystem stability and primary productivity were damaged to some degree and the steppe vegetation was in a continuous degenerate status at these sites.(3) The results of routine analysis of land degradation and radionuclide aesium-137trcing manifested:The main indexes of soil routine analysis, such as the physical property clay percentage, SOM and total N of soil routine analysis, they have the same change tendency with the average 137Cs area activity. This results demonstrated that the method of routine analysis and the technology of radionuclide aesium-137tracing can verify the research area land degradation situation well.
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