Temporal And Spatial Distribution Characteristics And Influencing Factors Of Soil Water And Carbon In Typical Small Watershed Of The Loess Hilly Region

As one of the most important soil components,soil organic carbon plays an extremely important role in maintaining soil fertility and soil health,while soil moisture is the most important limiting factor for vegetation restoration and agricultural utilization in semi-arid regions.Since the implementation of Grain for Green in the Loess Hilly Region for more than 20 years,Vegetation restoration plays an important role in carbon sequestration while reducing soil and water loss,but it also causes problems such as thickening soil dry layer and decreasing watershed runoff,which affects vegetation development and ecosystem stability.How to balance vegetation carbon sequestration and soil water consumption is a new problem facing Grain for Green in the new period.To meet the urgent needs of vegetation restoration and high-quality development of agricultural land use in the Loess Hilly Region,the main purpose of this paper is to explore the temporal and spatial variability of soil water and carbon in typical small watershed of the Loess Hilly Region.Four typical small watershed of about 1km~2were selected for small watershed investigation,UAV remote sensing,soil sample collection,and soil physical and chemical properties measurement.The spatial-temporal variation characteristics of soil water carbon and the impact of topographic vegetation on soil water carbon in small watershed were described and analyzed by combining classical statistics and geostatistics.Combined with topography,vegetation and soil texture of small watershed,multiple linear regression method was used to analyze the influencing factors of spatial and temporal changes of soil water and carbon in small watershed,and the main research results are as follows:(Ⅰ)The spatial and temporal distribution of soil water in different small watersheds in the Loess Hilly Region showed that the soil water content in gullies was significantly greater than that in the hills in May and October,while the heterogeneity of the gullies was more obvious in May,and the spatial distribution of soil water was mainly affected by structural factors.Terrain and vegetation types significantly influenced the spatiotemporal distribution of soil moisture in different terrain is characterized by the channel in state of high water content and rain after the incident,the channel change soil moisture content was more severe,different vegetation types was significantly changed the 0-100 cm soil layer soil moisture content,the difference between vegetation and natural conditions is more obvious,the higher the influence degree.(Ⅱ)The statistical characteristics and spatial distribution pattern of soil organic carbon in different small watersheds were significantly different in the Loess Hilly Region.With the decreasing of latitude extreme difference is greater than the average increase led to more discrete data distribution and the rapid increase of kurtosis positive skewness distribution trend is obvious,the heterogeneity of soil organic carbon content increased and increased;The spatial and temporal distribution of soil organic carbon was significantly affected by topography and vegetation type,and the soil organic carbon content of the same vegetation type was significantly different under different terrains.Topographically,there was a large amount of soil organic carbon accumulation in gully slope.In vegetation,woodland is larger than grassland and bare land.The soil organic carbon content in natural forest was significantly higher than that in plantation.(Ⅲ)At the small watershed scale in the Loess Hilly Region,the explanations of topographic and soil attribute factors to the distribution of long zui gou small watershed,Xi fu zi gou small watershed,Ren tai gou small watershed and Ma si chuan small watershed surface soil water content in May were 62.3%,61.5%,45.7%and 18.7%,respectively.The spatial and temporal distribution of long zui gou small watershed,Xi fu zi gou small watershed,Ren tai gou small watershed and Ma si chuan small watershed surface soil water content in October was explained by 54.0%,61.5%,68.5%and 29.7%,respectively.Topography and soil attributes all affected the spatial and temporal distribution of surface soil water content,and soil attributes were the main influencing factors of surface soil water content in different small watersheds.(Ⅳ)In the Loess Hilly Region,the spatial and temporal distribution of soil organic carbon content in long zui gou small watershed,Xi fu zi gou small watershed,Ren tai gou small watershed and Ma si chuan small watershed were explained by soil texture and topographic factors,which were 18.4%,22.6%,15.1%and 19.1%,respectively.