Temporal And Spatial Variation Of Soil Moisture And Its Influencing Factors In Arid And Semi-arid Areas Of China From 2000 To 2020

Soil moisture is a key factor affecting the growth condition and distribution pattern of vegetation,and is the most direct and effective water source that crops can absorb and utilize.However,the natural conditions in the arid and semi-arid regions of China are more severe,and the water content of the soil in turn determines the growth of vegetation and the production and construction of agriculture in the region.Therefore,the study of the spatial and temporal variation of soil moisture and the influencing factors in the arid and semi-arid regions of China is of great significance to the region in terms of agricultural drought monitoring,production activities,crop allocation and ensuring sustainable development of production and life.This paper used ESA CCI soil moisture data,combined with meteorological elements,NDVI,elevation,population density,land utilization,geomorphic type,soil types,vegetation types and other data,and used Theil-Sen trend analysis,Geo Detector and principal component analysis to quantitatively analyze the spatial and temporal variation of soil moisture and the influencing factors in this region.The results show that:（1）The average soil moisture in the study area was 0.18 m~3/m~3,and the overall interannual variation from 2000 to 2020 showed a significant upward trend at a rate of0.0005 m~3/m~3/a,but the variation of soil moisture in most areas was relatively stable.The seasonal variation pattern was high in summer and autumn and low in winter and spring,with obvious characteristics of dry and wet seasons.The spatial distribution showed a spatial pattern of"low in the north and high in the south,low in the west and high in the east,with the mountains higher than the basin",and the overall distribution was characterized by a gradual decrease from the periphery to the interior.Among them,the area showing a significant increase accounted for about 30.86%of the total area,and the area showing a significant decrease accounted for about 10.06%.In the future evolution trend,the regions that show a persistent and significant decrease accounted for about 6.7%of the overall,and the regions that show a persistent and significant increase accounted for about 14.5%.（2）In the arid and semi-arid regions of China,the univariate effect of soil types had the greatest influence on the spatial and temporal variation of soil moisture in this region.The two-factor enhanced interaction between soil types and elevation had the most significant effect on the spatial variation of soil moisture.The non-linear enhanced interaction between soil types and mean precipitation was the key factor affecting the trend of soil moisture.Regarding the spatial variation of soil moisture,the principal component analysis yielded that the relative contribution of temperature and potential evapotranspiration（PC1）to the spatial variation of soil moisture was 46.8%,that of NDVI and elevation（PC2）was 31.8%,and that of precipitation（PC3）was21.4%.In terms of variation trends,the relative contribution of temperature and potential evapotranspiration（PC1）was 59.4%,the relative contribution of NDVI and elevation（PC2）was 24.8%,and the relative contribution of precipitation（PC3）was15.7%.（3）The spatial and temporal variation of soil moisture was the result of a combination of factors such as soil types,temperature,precipitation,elevation,vegetation and potential evapotranspiration.Among them,topography,expressed by altitude,was the basic influencing factor of the spatial and temporal variation.Temperature,precipitation and potential evapotranspiration were the direct factors affecting the spatial and temporal variation of soil moisture in arid and semi-arid regions of China.The water content of the soil itself and the water-holding capacity of the soil also varied among different soil types,which also indirectly affected the spatial and temporal variation characteristics of soil moisture in the region.