The Characteristics Of Preferential Paths In Different Land Use Types At Simianshan In Chongqing

Preferential flow is a common form of soil water movement, which plays an important role in the transformation between surface water, soil water and groundwater. Study on the characteristics and its influence factors of the preferential paths in the different land use types, can provide a more reasonable theoretical basis for the protection and utilization of water and soil resources. The soil of different land use types on Simianshan in Chongqing were taken as the study objectives. Firstly, by applying brilliant blue dye tracing method, preferential flow was observed and then through using supervised classification and unsupervised classification method, according to the depth of dyed priority path was divided into 5 levels (1-5 level indicated the degree of staining in descending order),the characteristics of different levels soil preferential paths in different land use types, and the soil physical and chemical properties, the soil saturated hydraulic conductivity and root biomass were analyzed to reveal the factors affecting the formation of preferential paths. The results were as followed:(1) Preferential paths with different morphology in different land use types. Overall in forest land, the dyed area of preferential flow was the largest, transportion depth of water and solute in soil was the deepest, the connectivity of preferential paths was the best. The dyed area of preferential paths in different land use types ratio decreased with the increase of soil depth.(2) The percentage of dyed area of different levels of different land use types was different.. In wasteland, the largest proportion was 1st,5th level preferential paths, the lowest proportion was 3rd level preferential paths; in farm land, the largest proportion was 2nd level preferential paths, the lowest proportion was 5th level preferential paths; in forest land, the largest proportion was 1st level preferential paths, the lowest proportion was 4th level preferential paths. In the same soil layer, the dyed area ratio of the different levels of preferential paths with the change of the depth of the soil layer was: the preferential path with large aperture was reduced, while the preferential path with small aperture was increased.1st level preferential paths mainly existed in 0-10cm soil layer; 2nd、3rd level preferential paths mainly existed in 0-20cm soil layer; 4th、5th level preferential paths mainly existed in 0-20cm soil layer in wasteland and farm land, but mainly existed in 20-40cm soil layer in forest land.(3) Soil preferential paths of different land use types were subject to soil physical and chemical properties, saturated hydraulic conductivity and the root condition. The regression analysis showed that preferential paths dyed area ratio negatively linear correlated with soil bulk density, while positively linear correlated with total soil porosity, the number of root holes,and the correlation of soil organic matter content, saturated hydraulic conductivity, root weight density showed unitary quadratic equation. The dominant factors of preferential paths formed were soil physical and chemical properties, soil saturated hydraulic conductivity, root by principal component analysis, its influence from large to small order:organic matter content, root weight density, total soil porosity, saturated hydraulic conductivity, the number of root holes, soil bulk density.