Spatial And Temporal Variation Of Soil Moisture In The Source Region Of The Yellow River And Its Factors Of Influence

Huang Heyuan District is the source of the Yellow River in China and one of the important components of the Three Rivers National Nature reserve.The large area of the Yellow River source area,the topography in the region,the climatic conditions are complex,the comprehensive influence of various environment and man-made activity factors lead to the significant difference in the space of natural geographical factors such as soil moisture in the source area,to understand the spatial difference of soil water and its influencing factors in Heyuan District area,It is important to reveal the process and mechanism of soil water circulation in alpine region.This study selected the source area of the Yellow River as the study area,based on remote sensing soil moisture,combined with land cover,climate,topography and other data,to analyze the spatial variability of soil moisture in the 2000-2010 average and seasonal time scales;using linear regression analysis to quantify climate(precipitation and temperature),The influence of topography on soil water distribution and the influence of various environmental factors on the spatial differentiation of soil water by using principal component analysis method.Through the research,the following conclusions are drawn mainly:(1)The source area of the Yellow River is dominated by grassland cover types,and there is a positive correlation between surface soil moisture and vegetation cover,with weak spatial variability.The land cover type in the source area of the Yellow River is mainly grassland,and the soil water content generally shows the law of woodland > wetland > grassland > desert,gobi and bare land.The spatial variation degree of soil moisture under different cover types is quite different.On the time scale,the density of vegetation distribution is in direct proportion to the soil water content,and the soil water content is higher in areas where vegetation distribution is denser.(2)Soil moisture is positively correlated with precipitation and temperature in space.Precipitation is decreasing from north to south in space,and temperature is decreasing from east to west.The correlation between soil moisture and precipitation in warm season is significant,while the correlation between cold season and altitude is strong,and the correlation between average annual soil moisture distribution and altitude is relatively strong.In time,soil moisture has a strong correlation with precipitation.(3)Soil moisture has the opposite spatial distribution characteristics to altitude,and there are obvious differences in spatial variability.Soil water content generally shows as low altitude area > middle altitude area >high altitude area,and the spatial variability of soil water under different altitude gradients is low altitude area >middle altitude area > high altitude area.The spatial variability of soil moisture is higher in low altitude areas below 4000 m and lower in altitude areas above 5000 m.(4)The results of principal component analysis show that precipitation and altitude are the main factors affecting the spatial distribution of soil moisture in the source region of the Yellow River.Soil moisture has astrong correlation with precipitation and altitude,that is,soil moisture will change significantly with precipitation and altitude.The main factor affecting the difference of soil moisture distribution in warm season is precipitation,and in cold season when precipitation is scarce,the main factor is altitude.