Clay Mineral Compositions Of Soil On The Grassland And Its Environmental Significance

As secondary minerals during chemical weathering, clay minerals arecommonly found in various types of soil and sedimentary rocks, which areextremely sensitive to changes in the environment, so the combination ofcharacteristics of the clay minerals, mineral components and their contents changerecorded the clay minerals during the formation of a variety of changes inenvironmental factors from different angles.The article based on alpine meadow soil in the Qinghai-Tibet Plateau and theInner Mongolia steppe soil as the research objects and selected different vegetationtypes、parent material and topography parts of the soil profile, through comparing thetwo study areas combination of features and content, soil mechanical composition,soil organic carbon and many other indicators change by using high-resolutionsampling, analyzing the relationship between various indicators, then explore thedifferent grassland ecosystem type of weathering and climate characteristics,revealing the environmental significance of clay minerals on the grassland soil.Some conclusions are as follows:(1) The Qinghai-Tibet Plateau and Inner Mongolia soil profile of grain sizeare denominated mainly silt, above the90%of the total content, but clay content lessthan10%, which reflecting the low degree of soil development and the weakweathering and pedogenesis. In the Qinghai-Tibet Plateau region, Bangor County mountain slope foot of clay soil silt content was significantly greater than themountain slopes because of topography; the Naqu soil sticky silt content wassignificantly greater than the Bangor County plots，meanwhile soil is finer particles,which mainly due to the impact of the vegetation types, the alpine shrub meadowstrong water storage capacity and high vegetation coverage are two reasons. In theInner Mongolia region, Sunitezuoqi desert steppe soil increased with increasingdepth， but sand content decreased, reflecting soil transformation in the arid,semi-arid areas of wind erosion；however, the Abagaqi grassland soil particle sizevariation with depth is not obvious, the surface soil is almost the original particlesize characteristics.(2) The Qinghai-Tibet Plateau SOC content was significantly greater than theInner Mongolia because of lower annual average temperature, the higher the averageannual rainfall, soil moisture, and a longer freeze time. Bangor County foothills SOCstorage was significantly greater than the slope, which high clay content plays aprotective role in the formation and stabilization of soil organic carbon. By a numberof factors as temperature, precipitation, vegetation type coupling effects lead to SOCstorage Naqu County is far greater than the Bangor County. Moreover, the SOCstorage capacity of Abagaqi is significantly greater than Sunitezuoqi showed thatSOC storage capacity tended to decrease with the increase in temperature anddecrease in precipitation.(3) The main clay mineral composition are illite in the Qinghai-Tibet Plateauand Inner Mongolia, more than70%of the total content，the others are chlorite,kaolinite, similar content, and essentially free of Smectite. The clay mineralassemblages characteristic, illite chemistry index (ICI) and the illite crystallinity (IC)shows the cold and dry climate characteristics, so study area are mainly physicalweathering and weak chemical weathering. By comparing the clay mineralscharacteristic changes of alpine grassland soil，forest grassland soil and tropicalforest soil, which indicating the clay mineral assemblages has obvious zonaldistribution characteristics, climatic conditions is the primary factor in control ofchemical weathering, tectonic activity and the nature of the parent rock are secondary factors, but still have important impact on the intensity of chemicalweathering. Two Study area soil samples are detected the presence of a small amountof kaolinite, these may be derived from eolian deposition, also may be sedimentaryrocks released some kaolinit by physical weathering.