Characteristics Of Soil Moisture And Its Main Influencing Factors In Different Hydrological Years In Western Shanxi Loess Region

The ecological environment in western Shanxi loess region is fragile,and the soil moisture conditions are related to the vegetation restoration.Therefore,exploring the characteristics of soil distribution on slopes is a necessary foundation for the rational use of land resources.In this study,the natural forestland,the artificial forestland,and the grassland in the Caijiachuan watershed in western Shanxi loess region were the main research objects.Based on field location observations and indoor experiments,the temporal and spatial surplus and loss of soil moisture on slopes and the characteristics of vegetation’s use of soil moisture are explored,so as to provide a theoretical basis for vegetation restoration in this area.The following conclusions were obtained:(1)The distribution of soil moisture characteristics of forestland were similar in soil profile.Thesoil water content of natural forest and artificial forest decreased with the increase of soil depth,while grassland was opposite.In the consecutive hydrological years,the soil moisture of the artificial forest is more severe than that of the natural forest,and it is difficult to recover in the wet year,and the soil moisture deficit under the downhill is more serious.The soil moisture condition of the grassland is better,and the phenomenon of desiccation occurs less.(2)Soil moisture deficit occurs in different vegetation types in drought years.In the normal or the wet hydrological year,soil moisture can be recharged,especially in a wet year,natural forests show high recharge in different slope positions,while the recharge depth in the middle and in the bottom of the slope in the grassland can reach 400 cm.The main factors affecting soil water storage in the 0～100cm soil layer are vegetation type and topography,while for the 100～200cm soil layer,capacitance and topography dominate the variation of soil water storage,and for the 200～400cm soil layer,soil texture,capillary porosity and organic carbon content are the key factors dominating the variation of soil water storage.(3)Heavy rain provides a higher degree of replenishment of soil moisture than light rain,and the surface soil moisture changes drastically after rain.When the rainfall is small,the infiltration depth of the artificial forest is greater than that of the natural forest,and when the rainfall is about 120 mm,the soil moisture infiltration depth of the natural forest is greater than that of the artificial forest.There is a significant positive correlation between precipitation amount,precipitation duration,infiltration amount and infiltration depth.There is a positive correlation between early soil moisture and infiltration depth of soil moisture.(4)There are differences in the main water sources of vegetation in different months of the growing season: at the beginning of the growing season(May)the main water absorption layer is the surface layer,and in July the main soil water use layer deep.The soil water use layer of natural forest is the largest and deepest,the deepest can reach 240 cm.Natural forests have more survival advantages than artificial forests under drought conditions.In artificial vegetation,Platycladus orientalis still maintains a high soil moisture in the deep layer during dry years,while the main soil moisture absorption layer of Robinia pseudoacacia is relatively flexible.