Spatio-temporal Distribution Of Soil Moisture In The Slope-gully System Of Northern Loess Plateau

Soil moisture is one of the most important factors restricting vegetation growth in loess area of northern Shaanxi,because of its broken terrain,serious vegetation degradation and more complicated soil water condition under the interaction between topography and vegetation.The soil moisture is one of the most important factors that restrict the growth of vegetation in loess area of northern Shaanxi.Slope ditch system is a typical terrain unit of the Loess Plateau and the main site of soil and water loss.Its development not only splits the surface of the earth,destroys the cultivated land,but also silts up the river and fills the reservoir.It is helpful to fully understand the characteristics of soil reservoirs in loess area and clarify the role of soil moisture in slope-gully system.It is of great scientific significance for ecological construction and water resources management to study the spatial and temporal distribution of soil moisture in topographical broken basins.In this paper,41 observation points on 4 sample lines of broken terrain in Shenmu Liudaogou Basin were used to observe the water status of soil profile for a long time,and the temporal and spatial distribution of soil moisture in the cross section was analyzed.The temporal and spatial dynamics of soil moisture and the distribution of soil available water in deep soil are studied.The main conclusions are as follows:?1?The soil water content of the north cross section is larger than that of the south side,and the average soil water content of the south cross section is only 15.69%.The temporal and spatial variation of soil water storage in the south side is basically consistent in size and order.The water storage capacity presents the characteristics of S_3.6-4.6>S_2.6-3.6>S_1.6-2.6>S_0.6-1.6?The water content of the soil is positively related to the content of the clay?p<0.01?,there was a significant negative correlation between sand content and grain content?p < 0.05?,it was negatively correlated with altitude?p < 0.01?.There is a linear correlation between the water storage on both sides of the cross section and the distance between the furrow edge and the furrow edge.Due to the existence of lateral evaporation,the soil water content at the far edge of the ditch is larger than that at the edge of the furrow.On the south side of the cross section,there is a slight dry layer.The average water content,thickness and initial depth in the dry layer are 11.35%,0.89 m and 1.32 m,respectively.?2?The soil water content of channel,edge and slope is in the order of channel > edge > slope,and the seasonal and inter-annual distribution of soil water storage is obviously different under different terrain conditions.The variation degree of soil water storage in each slope is different under the three topographical conditions.The spatial variation of average soil water storage is as follows: downslope >middle slope > slope;The depth of distribution curve and extreme value of soil water content at each observation point is different.Soil desiccation occurs in all three topographical conditions.Soil texture?clay,silt,sand?and relative altitude have certain correlation with soil moisture content under slope and ditch system.?3?The soil available water content in gully,edge and slope was as follows: channel > slope > gully edge.Soil water storage on gully edge and slope showed different degrees of deficit,and the water surplus in non-growing season was higher than that in growing season.The order of vegetation water use efficiency and vegetation precipitation utilization efficiency in different growing seasons is slope > gully edge >channel.The available water content in 0¹ m soil layer on the edge and slope of the growing season is lower than that in the channel soil,and the available water content in the channel soil is more abundant.The content of soil available water in the growing season showed that the content of soil available water decreased in the shallow layer and increased in the deep layer.The available water supply in the surface soil in the non-growth season was obviously faster than that in the deep layer,showing the distribution characteristics of the high available water in the shallow soil and the low available water in the deep soil.On the spatial scale,the effective water content of 0² m soil layer varies greatly under the three topographic conditions.