| This research throug observation to the soil moisture of different parts of sandy region in Yanchi County of Ningxia province, discussed the dynamic changes of soil moisture of different parts of sandy region and the Formation laws of the Dried Sand Layer. The results as follows:(1)Affected by rainfall, there are large exist of soil moisture changes of 0～200cm in different months. The Sand dunes can be divided into three tiers in 4～10 mouth in 2007:the accumulating stages in 4～6 mouth,consuming stages in 7～8 mouth and the second accumulating stages in 9～10 mouth. From the vertical distribution,there ara different lays about the soil moisture in different samples and seasons. The Sand dunes can be divided into three layers:dry sand layer,active soil moisture layer and stable soil moisture layer according to the characteristics of soil moisture.(2) The rainfall infiltration depth changes with the rainfall at Yanchi Sandland.but the rainfall under 5mm can not be used by the vegetation in desert. The rainfall plays a very important role in the water cycle Only when the rainfall is greater than 10mm.Because of the inhibitory effect of dry sand layer,the water Added the groundwater apart some evaporation when the rainfall is greater than 15mm.(3) The heat is difficult to transfer to the lower sand,when the heat capacity and thermal conductivity is reduced because of the Reduction of the soil moisture with the increasing evaporation after rainfall. The water can not be added to the soil surface thouth the Capillary because the capillary water rise height is lower. The evaporation of soil moisture migration with Water vapor diffusion,so form the dry sand layer.(4) The gradual development of dry sand layer has a significant inhibitory effect on the evaporation of soil moisture. And more thick the dry sand layer is, stronger inhibitory the sand water evaporation is.So we should retain a part of large-scale flow in sand,because it has a very important role to protect the sand water. |
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