Impacts of fractal features on moisture infiltration of soil of typical forest stands of Jinyun Mountain in Chongqing,southwestern China

The soil structure is expressed with fractal dimensions of particle size distribution(PSD),aggregate size distribution(ASD) and soil pore size distribution(SPD).The effect of soil fractal features on soil infiltration velocity and its process was studied.The result of the fractal feature shows that fractal dimensions of PSD is obviously greater than that of ASD and SPD,and in different soil genetic horizons,the fractal dimension of ASD has the greatest variability,and takes on down trend from top to bottom genetic horizon.According to the soil infiltration process curve,the infiltration process is divided into 3 phases,1) the initial phase(0-5 min),2) the transition phase(5-30 min) and 3)the stable phase(30-180 min).In the initial phase of infiltration, the soil structure of A₁ soil genetic horizon was the major influencing factor;in transition phase of infiltration,the pore distribution of AB horizon and soil structure of B horizon were the major influencing factors;in the stable phase of infiltration,the soil structure of C horizon is the major factor affecting the infiltration velocity.Soil infiltration process is influenced comprehensively by soil PSD,ASD and SPD.In the whole soil water infiltration,the infiltration of shrub forest land was much faster than other forest lands;in the initial infiltration phase,arable land soil infiltration was far faster than forest land;in the stable infiltration phase,the infiltration velocity of forest land was faster than arable land.