Study On Soil Moisture Characteristics Under Different Vegetation Types In Shenmu County

Shenmu County is located in the southeastern margin of the Mu Us desert,suffering from wind erosion damage,the government have taken afforestation measures for many years,so that the problem has been effectively solved.However,the area is a typical arid and semi-arid area with limited and centralized precipitation,which makes soil moisture to be an important factor to limit vegetation growth.Moreover,vegetation growth affects water cycle.In this thesis,taking the soil moisture under different vegetation types as our research target,research of the correlation and heterogeneity of the soil moisture in different land types.Discussing the effects of vegetation types and soil physical and chemical properties on soil moisture,which has a certain reference for the scientific use of water resources and the promotion of vegetation restoration.In this thesis,the soil moisture and related data of soil physical and chemical properties were obtained by reading literature,designing experimental,collecting field soil sample and experimental analysis.Through the use of SPSS,GS +,SAS and other software to analyze soil moisture data.What's more,the relationship between soil moisture and vegetation type,soil organic matter and soil particle size was discussed.Finally,establish the soil moisture prediction model.The main contents and conclusions are as follows:First of all,study the characteristics of vegetation community under different land use types.Artificial forestland was named Pupulus simonii,artificial shrub land was named Salix psammophila shrubsand,artificial grassland was named Allium mongolicum grassland.The distribution characteristics of soil moisture in 0?70cm section under different vegetation types were analyzed.The soil moisture content in the study area was between 3.42%?5.66%,the order of the soil moisture was Allium mongolicum grassland(5.66%)>Salix psammophila shrubs(4.57%)>bare sandy land(4.15%)>Pupulus simonii(3.42%).As the sampling area of bare sandy land is at low slope positions,precipitation is concentrated in July and soil moisture is gathered,so the average moisture of bare sandy land is higher than Pupulus simonii.Soil moisture under the four types of land belongs to moderate variation.The vertical distribution of soil moisture shows that the variation of soil moisture content along the vertical profile is fluctuating.The change trend of soil moisture content in the Pupulus simonii were in the form of wave,the highest soil moisture content was 5.55%,in 50?55cm soil layer.The soil water content of Salix psammophila shrubs overall showed a trend of decrease type,the soil moisture began to increase from 55cm depth,and the maximum was at 65?70cm.The content was 6.42%.The change of soil moisture in the Allium mongolicum grassland showed a growth trend,the maximum was located in the soil layer of 60?65cm,the content was 7.45%.The change of the soil moisture in the bare sandy land was in the form of stable trend,and the maximum value was in 25?30cm,at the content of 6.33%.Nugget base value shows soil moisture in Allium mongolicum grassland,Salix psammophila shrubs and Pupulus simoii showed a strong spatial auto-correlation,space auto correlation distance is 0.27m,0.26m and 0.37m.Soil moisture of bare sandy land showed a medium spatial auto-correlation,space auto correlation distance is 0.23m.For Allium mongolicum grassland,Salix psammophila shrubs and Pupulus simoii,the optimal fitting model of soil moisture is spherical model,for bare sandy land,the optimal model of soil moisture was the linear model.The soil particles in the study area are mainly composed of fine sand and medium sand,which contains a certain amount of powder,very fine sand and coarse sand,and the content of clay is the least.The average content of soil organic matter in different vegetation types is between 1.47g/kg-?3.55g/kg,the order in different sections is Pupulus simonii>Salix psammophila shrubs>Allium mongolicum grassland>bare sandy land.The pH of soil was between 7.8 and 8.21,they are all alkaline soil.the order in different sections is Pupulus simoii>Salix psammophila shrubs>Allium mongolicum grassland>bare sandy land.The average content of iron in the range of 1.14g/kg?1.81 g/kg,the average content of copper in the range of 1.27mg/kg?4.54mg/kg,the average amount of manganese in the 118.51mg/kg?228.83mg/Kg,the average content of zinc in the range of 8.06mg/kg?15.73 mg/kg,they were significantly lower than the national background value.The correlation coefficient showed that there was a significant positive correlation between soil moisture and fine sand in the Pupulus simonii,which was negatively correlated with the powder,medium sand,coarse sand and organic matter,and was positively correlated with pH,which was not related to the trace elements.In Allium mongolicum grassland,there was a significant positive correlation between soil moisture,clay and fine sand.And negatively correlated with three kinds of trace elements such as coarse sand,organic matter,Fe,Mn and Zn,and not correlated with pH.In Salix psammophila shrubs,there was a significant positive correlation between soil moisture and grain size,and negatively correlated with organic matter,there was no correlation with pH and trace elements.There was a significant positive correlation between soil moisture and fine sand in bare sandy land,and negatively correlated with organic matter,which was not related to pH and trace elements.Using SAS multiple regression analysis to establish the prediction model of soil water content in different vegetation types.Through the system test,the accuracy of the prediction model of Pupulus simoii was more than 87.73%,Salix psammophila shrubs was above 84.09%,Allium mongolicum grassland was more than 90.93%.Precision of the prediction models are high in all vegetation types.