Study On Soil Desiccation Dynamic Of Natural Grassland And Its Response To Precipitation Change In Yunwu Mountain,ningxia,China

In order to study the dynamic mechanism of soil drying in natural grassland in semi-arid area of Loess Plateau,this experiment took the natural grassland of Yunwu mountain in Ningxia as the research object,with different land use methods(grazing grassland,enclosed 15 years of grassland,15 years of caragana korshinskii and enclosed 30 years of grassland)and precipitation changes(50%precipitation,100%precipitation and 150%Precipitation)as treatments,to analysis of deep soil moisture characteristics,and soil drying dynamics and influencing factorsof natural grassland on semi-arid area of the Loess Plateau with mathematical statistical methods.The results showed that the initial depth of soil dry layer was 80,100,120 and 360 cm in grazing grassland,enclosed 15 years of grassland,15 years of caragana korshinskii and enclosed 30 years of grassland,respectively,the dry layer thickness was 380,180,120and 100 cm,respectively,and the average water content of soil in the dry layers was 9%,8.9%,8.1%,9.7%,respectively.The soil profile of four kinds of land use types showed different degree of drying phenomenon,soil drying of grazing land and 15 years of caragana korshinskii are the most serious,enclosed 15 years of grassland 0-500 cm soil water content is significantly higher than grazing grassland(P<0.05),the soil moisture content of enclosed 30 years of grassland 0-500 cm layer was significantly higher than that of grazing grassland(P<0.01).And under 50%,100%and 150%precipitation of fencing 15 years grassland,the formation depth of soil dry layer begin at 100,180 and 280 cm respectively,and the thickness was 400,320 and 220cm respectively.The average water content of soil in dry layer was 5.2%,5.11%and 4.57%,respectively,and the average water content of soil was 6.31%,8.83%and 10.25%,respectively.Therefore,precipitation significantly affected soil moisture,0-500 cm soil profile water content decreased with the decrease of rainfall,the increase of precipitation significantly decreased the degree of soil drying,in fencing 15 years grassland;The fencing measures had a positive effect on the elimination of soil dry layer,long-term fencing(30 years)will weak soil drying,but less than15 years fencing,the dry layer of soil still exists;the drying degree of shrub(caragana)planting soil is significantly higher than that of grassland,and the relief of soil dry layer is not only affected by the recharge of soil moisture from precipitation,but also by deep soil moisture and vegetation cover.Therefore,the dynamic of soil dry layer in semi-arid area of Loess Plateau is subject to rainfall change and vegetation difference.