| Mountainous areas account for69%of the total land area in China, while dual slope accounted for the major part in mountains. These slopes in the condition of continuous water supply are proned to subsurface flow. It damaged to the integral and stable of the sloopes as well as subsurface flow occurs at the same time be accompanied by nutrient loss. Therefore, the research of characteristics of runoff of subsurface flow and characteristics of nutrient leaching in the mountain complex slopes give a theoretical foundation for quantitative calculatton of runoff rate of subsurface flow with different slopes.This paper focused on the three dimensional adjustable soil flume, combinatton with uniform and no ponding. Infiltration to study the impact, which is different combinations of slope effects of characteristics of subsurface flow as red soil which is developed by the Quaternary clay and yellow brown earth which is developed by sand shale. And by the infiltration experiment, to study characteristics of soil nitrogen loss at two soils in continuous leaching conditions. Using statistical methods to draw the following conclusions:(1)For red soil, in the case of water supply constant, alpha(transverse slope) staying the same and beta(longitudinal slope) growing gradually, runoff rate of subsurface flow at of the SA(20cm layer of transverse slope) and SB(40cm layer of transverse slope) grows with beta increases. While beta increases runoff rate of subsurface flow at of the LA(20cm layer of longitudinal slope), LB(40cm layer of longitudinal slope) and C (45cm of bottom layer) decreased conversely. In the whole process of infiltration, every overland flow yield occupies different proportion owing to different slopes combinations. The proportion of subsurface flow at of the SA and SB increases with the increases of beta, while at of the LA, LB and C it decreases gradually.(2)At different sloopes combinations, runoff rate of subsurface flow showed a significant impact for red soil at of the SA, SB and LB, and fitted equations have been given. From equations, we can learn that, runoff rate of subsurface flow at of the SA is positive correlation with beta, and it is negative correlation with alpha, and it has larger effect on the runoff rate of subsurface flow at beta. Simultaneously, runoff rate of subsurface flow at of the SB is positive correlation with beta, and it is negative correlation with alpha, and it has larger effect on the runoff rate of subsurface flow at beta. Runoff rate of subsurface flow at of the LB is negative correlation with beta, and it is positive correlation with alpha, and it has larger effect on the runoff rate of subsurface flow at beta. The equations will provide theoretical foundation for quantitative calculation of runoff rate of subsurface flow with different slopes changing.(3)For Yellow brown soil, in the case of water supply constant, alpha staying the same and beta growing gradually, runoff rate of subsurface flow at of the SA and LA are not significantly changed. And their values are very low even have no value with beta growing bigger. Runoff rate of subsurface flow at SB grows while beta increases at LB and C decreased conversely. In the whole process of infiltration, every overland flow yield occupies different proportion owing to different slopes combinations. The proportion of subsurface flow at SA and SB increased with the increase of beta, while at LA and C it decreases gradually and at LB it changes not obviously.(4)At different slopes combinations, runoff rate of subsurface flow showed a significant impact for Yellow brown soil at of the SB, LB and C, and fitted equations have been given. From equations, we can learn that, runoff rate of subsurface flow at of the SB is positive correlation with alpha and beta, and it has larger effect on the runoff rate of subsurface flow a beta. Simultaneously, runoff rate of subsurface flow at of the LB is negative correlation with beta, and it is positive correlation with alpha, and it has larger effect on the runoff rate of subsurface flow at alpha. Runoff rate of subsurface flow at of the C is negative correlation with alpha and beta, and it has larger effect on the runoff rate of subsurface flow at alpha.(5)Under the combination of different slopes, runoff rate of subsurface flow has a significant difference between soil red and yellow brown soil. For red soil clay is higher and heavier, so soil moisture in red soil flows slower than in yellow brown soil. Red soil is easily affected by lateral slope.As a result, in0-20cm layer, runoff rate of subsurface flow and speed of subsurface flow are both higher than yellow brown soil;in20-40cm layer and bottom layer, runoff rate of subsurface flow and speed of subsurface flow are both lower than yellow brown soil. The speed of subsurface flow response and the constant flow rate are higher than red soil too. For yellow brown soil, subsurface flow mainly move downward and infiltration capacity at bottom layer accounts for more than60%of the total subsurface flow yield, and compared with gentle slope, it can even exceed80%.(6) Under the condition of dual slope, the law of nitrogen leaching forms is different with the different soils. The losses of available nitrogen in red soil are concentrated in nitrate leaching, which accounts for75%～86%of total amount of leaching. Available nitrogen form in yellow brown earth has smaller difference, ammonium nitrogen accounts for37%～42%, nitrate nitrogen accounts for58%～67%. |
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