A Study On The Response Of Runoff And Sediment And The Characteristic Of Physical-Chemical Of Soil On Karst Slope

The special binary structure(surface-underground)in karst area that has changed the way of the water loss and soil erosion,the variation characteristic of physical-chemical of soil.Based on the above situation,This paper was researched characteristics of runoff and sediment yield in the karst slope and the influence of changes of soil physical and chemical properties under degree of underground fissures and rainfall,surface different treatments(the grass land,the bare land,the bare rock)through the nature rainfall.The test results show that:(1)Under the condition of different rainfall,runoff on the space allocation were given priority to with surface runoff.Correlation analysis were very significant negative correlation between surface and subsurface runoff coefficient and there was reciprocal relationship.The rainfall influenced the way of sediment on the karst slope.In general,the leakage of soil was main way of sediment yield during small rainfall.With the increasing of rainfall,the sediment yield of surface slope gradually became the main way of sediment yield on the karst slope.There was a critical point of rain at 0.83mm/h~1.07mm/h,which caused the surface sediment yield beginning to exceed the sediment yield of the underground.Due to the development of the underground crack degree and different surface,the characteristics of the runoff and sediment on the karst slope were not single increasing or decreasing.(2)The degree of fissure and different surface affected the loss characteristics of the soil nutrients.That showed:(1)In the fissure of 3-8%,the loss of AN of surface and underground were greatest and the loss peak appeared on the fissure of 8%,suggesting that nitrogen was easy to loss.The fissure of 5% was critical point that the loss of AK the surface and the underground decreased or increased.The fissure of 5% was most likely to lead to the loss of AP on karst slope.The development of the underground fissure was not the main factor resulting in the loss of SOM but only influenced the loss concentration of SOM.(2)The loss concentration of AN,AK were higher than that of AP,SOM.(3)The loss concentration of AP of the surface and the underground of the grass were greater than that of the bare land and the bare rock.But its the loss concentration of AN was the lowest.When in the fissure of 3%,the loss concentration of AK of the surface and the underground of the grass and bare land were greater than the bare rock.But the loss concentration of AK of the bare rock was lower than the grass and the bare land in the fissure of 5%.The characteristic of the loss concentration of the surface and the underground of SOM were relatively complex.When the fissure of 3%,the loss concentration of SOM of the surface and the underground of the bare land and bare rock were higher,that of the surface of the grass was lowest,while the loss concentration of the underground of the grass was the largest.(4)The loss concentration of AP,AK,AN,SOM of the surface were greater than that of the underground.(3)The degree of fissure and the different surface had different influence on the change of the soil particle composition of the surface and the underground erosion for different porosity on the surface.That showed:(1)The clay and silt content of the surface showed a trend of increasing and reached the maximum in the fissure of 8%,while sand content showed a trend of decreasing and got to the maximum in the fissure of 5% with the growth of underground crack degrees.The clay and silt content of the underground fist increased than decreased and reached the maximum in the fissure of 5%,the sand content increased before decreased and got the maximum in the fissure of 3%.Under the(3)three surface conditions,the clay and silt content of the sediment of the underground and surface higher.The three kinds of the soil particle composition of the surface and the underground also different under the same fissures.