Soil macropore characteristics of different reclaimed mine soils in dump of surface coal mine

There are a large number of macropore and tubular channels with a diameter of several centimeters and plant roots in the reclaimed soil of dump and which were the main reason for the formation of soil macropore and soil preferential flow. The radius,number and distribution of soil macropores under the different reclaimed vegetation(Rob- inia pseudoacacia,elm,mixed forests (Robinia pseudoacacia and elm),shrub,farmland and weeds)in the dump were investigated using water breakthrough curve and Poiseulle equation. The results showed that:① The characteristic of water breakthrough curve differed significantly and the steady effluent rate of 0 - 5 cm soil layer was 0. 0193-0. 0315 mm / s among the different reclaimed vegetation;the steady effluent rate of arbor forest was higher than shrub land and weeds. ② The water breakthrough curve showed a trend of increasing sharply first then staying stable and having different characteristics in different periods with active period,fluctuation period and stable period;Gravel and vegetation root system are the main reasons for the fluctuation of water breakthrough curve. ③ The steady effluent rate was decreased with the increase of soil depth,and which of 0-5 cm soil layer was maximum,0. 019 3-0. 031 5 mm / s and 50-60 cm soil layer was minimum,0． 002 8-0． 003 5 mm / s. ④ The radius of soil macropores ranged from 0. 03 to 4. 71 mm and the soil macroporosity ranged from 0. 03% to 16. 58% under the different reclaimed vegetation in the dump;the mean radius determined 65% variances of steady effluent rate and 42% of saturated hydraulic conductivity.