Xi'an Region Apple Woodland And Farmland Soil Moisture Change Research

The Loess Plateau is situated at semi-humid area,where the rainfall is little and concentrates, and the underground water buried depth is deep,which cause the soil moisture to be especially important in vegetation construction of the Loess Plateau.Surface evaporation and plant's transpiration cause the soil moisure to be serious lost,and the dry layer has appeared in soil under some vegetation.The moisture content is the most important factor that restricts northwest ecological environment construction and the important factor that restricts the development of the agriculture and the forestry,so the research to the soil-water environment in the artificial vegetation has the extremely vital significance.Through determining the soil moisture in different artificial vegetation from the surface to below 6 meters in Xi'an area of the most south of the Loess Plateau,this artical has studied some problems such as in local area the soil moisture content' seasonal variation in farmland and apple forest land in 2008,the region difference of different artificial vegetation,the soil moisture variation condition of the farmland,the soil moisture consumption process of the apple forest and so on.The samples studied are got through light-duty manpower.The depth of the hole is 6 meters,and the distance is 10 centimeters.In every hole 60 samples are got.The determination of the soil moisture content uses the drying weight method which is considered accurate and reliable.The spots include the university city and Shaoling plateau in Chang'an area,Pangxi village in Xianyang area, as well as Liquan and so on.Kinds of the artificial vegetation were chosen including the 7 age,10 age,15 age apple forest,the wheat and the corn and so on.Through the determination and analysis to soil moisture content of apple forest and farmland in the different seasons,we have obtained the below knowledge.(1) The soil moisture content under different artificial vegetation of Xi'an area is different. Among the artificial plant chosen by us,average of soil moisture content of farmland is 16.95%.,for ten-year-age apple tree plantation,it is 14.61%which is less than farmland's by 2.34%.In the depth of 0-200cm,200-400cm and 400-600cm,average of soil moisture content of farmland is 14.63%, 17.10%and 19.12%,for apple tree plantation,it is 13.63%,15.01%and 15.18%.Above data show that water consumption of apple tree plantation is more than farmland.(2) Different age of apple forest have obvious difference in soil moisture content.The Young age of soil moisture of apple forest is higher than middle age.In the same condition of terrain,for 6 m,soil mositure of different age apple forest have same resemblance that is changed by depth..(3) In autumn of 2008,the soil moisture in "universities city",Pangxi village and Shaoling Plateau was measured and obtain the result that Shaoling plateau is the highest then is universities city the last is Pangxi village.In Pangxi village and Liquan,the middle age of soil moisture of apple forest is generally low,which is 11.42%and 12.94%.And soil moisture of below 4m of middle age generally is less than 12%.This evidence adequately shows that soil of middle age of apple forest in this area generally has dry layer.(4) In half century climate of Xi'an is apt to warming and drying.From 2003 year having enough precipitation to now,soil moisture of farmland still remains high.Farmland has no dry layer even at high peak of water consumption of wheat,soil moisture also meet need of crop growing. This evidence is related with normal precipitation during these 6 years in this area.The conclusion is that soil moisture is influenced by precipitation in short period.(5) Precipitation in Xi'an,2007,is 698.5mm,enough rainy water year.After 2008 consumption,soil moisture of 15-year-age apple forest obviously decreased.The conclusion is that the consumption speed of the soil moisture under middle age apple forest land in Xi'an area is very quickly,moreover it is difficult that only depending on the precipitation in the rainy year to maintain the middle age apple forest' normal growth.(6) By minor 2 multiplications to simulate fluctuation of 0-6cm soil moisture content for different artificial vegetation,the finding isφ=c₁+c₂z+c₃z²+…+c₆z⁵,this algebraic expression with five terms can evaluate the soil moisture.(7) By the mode of soil moisture dynamics,simulate and contrast fluctuation of semi-humid area of soil moisture in Chang'an district of xi'an from 25^th,March,2008 to 8^th April,2008,the deviation is 0.0078.Data is very near to reality.The simulating data of 0-1m of surface soil is poor because of strong sensibility of soil moisture dynamics for root distribution,diffusivity of soil moisture and conductivity.