Study On Spatial Variability Of Soil Physical Properties In Qinba Mountain Area

The ecosystem of Qinba mountain area is fragile,which has serious land desertification and soil erosion.Regional soil physical properties vary greatly in space,systematic understandings and analyses on the regional distribution characteristics of soil physical properties are of great significance to the improvements in agricultural production and ecological environment.Therefore,this study collected soil samples from three north-south crossing zones in Qinba mountain area,then measured the soil physical attribute parameters based on the field investigation and laboratory analyses.The pearson correlations and descriptive statistical characteristic indexs of soil hydrological factors in three sample zones were analyzed by traditional statistical method.Calculating and determining the spatial distributions and longitude-latitude variations of soil hydrological factors by the semi-variance function,and the minimum data sets of soil moisture content and bulk density between three sample zones was obtained according to the principal component analysis(PCA).Based on it,the interactive relations of soil physical properties in Qinba mountain area were determined,and the driving factors of soil moisture content and bulk density were studied,which further constructed the related multiple linear regression models.The conclusions are as following:(1)The mean values of soil moisture content in Qinba mountain area ranged between 17.74%-22.40%,which belongs to weak variability;the saturation moisture contents varied from 34.43%-38.25%,which the results of western route belongs to medium variability while the mid-eastern route has weak variability;the soil available water contents were between 11.13%-16.19%,which the east-west route belongs to medium variability while the middle route has weak variability;the average soil bulk density ranged from 1.26g/cm3-1.41g/cm3,which the west route belongs to medium variability while the mid-eastern route belongs to weak variability;the mean values of saturation conductivity coefficient ranged from 0.15 mm/min-0.31mm/min,which the west route belongs to medium variability and the mideastern route has weak variability;The average p H values were between 5-8,which the west route belongs to high variability and the mid-eastern route has medium variability;the organic matter contents were between 10.12g/kg-21.59g/kg,which the middle route belongs to high variability,the west route belongs to medium variability and the east route has weak variability;the soil in this area is mainly composed of loam.(2)The mean values of soil moisture content,saturation moisture content and available water content were largest in grassland among all the different land use patterns of three north-south crossing zones,while the farmland had the weakest spatial variability;farmland had the maximum soil bulk density and organic matter content;There were no significant differences in soil saturation conductivity coefficient,particle composition and p H value,indicating that vegetation type had less influence on the soil.(3)There were relatively low values of soil moisture content,saturation moisture content,available water content,bulk density,p H and organic matter content appeared in N32.5?-N33.0?.The values of p H and organic matter content of the north were higher than the south,while the values of rest above parameter were higher in the south but lower in the north.As for the spatial distribution patterns of regional soil properties,the soil moisture contents showed clustered distribution which were lower in the east but higher in the west;The soil saturation moisture contents decreased first and then increases from east to west;the soil available water contents were lower in the east but higher in the west,which gradually decreased from west to east;The soil bulk density had the opposite distribution pattern of saturation moisture content,while the patterns of soil saturation conductivity coefficient were similar to saturation moisture content;The spatial distribution pattern of sand particle and organic matter contents was similar,which was higher in the east but lower in the midwest,while the pattern of p H value was opposite.(4)There were extremely significant correlations with soil hydrologic parameters(including soil moisture content,saturation moisture content,available water content and saturation conductivity coefficient)in Qinba mountain area,and each hydrologic property had a negative correlation with soil bulk density,indicating that there were interactions between hydrologic properties and soil bulk density.In addition,rainfall had significant impacts on surface soil moisture while the altitude variations had greater impacts on soil bulk density.The main driving factor of soil moisture is soil bulk density while the main driving factors of soil bulk density are soil moisture,available water content and saturation conductivity coefficient.The multiple linear regression models of soil moisture content and bulk density had relatively good predictive effects,while compared with soil moisture content,there was a better fitting degree in soil bulk density.