Analysis Of Soil And Water Loss Process And Control Factors In Slope Land Of Karst Trough Area

Slope land is the most basic geographic unit and also the most important source of soil erosion.At the same time,slope land is also the fundamental geographic unit of karst trough and valley.Quantitative evaluation of the runoff generation and ion loss process in the karst trough valley is the key tool to prevent and control rocky desertification.It is also the basis for the study of soil erosion mechanism model in karst trough areas and the fundament of making reasonable strategies for soil and water conservation.Soil erosion causes serious ecological and environmental problems,which reduces the area of cultivated land in the western region,degrades the land quality and seriously affects the effective use of water resources,and aggravates the development of drought;resulting in vegetation degradation,rock exposure,rocky desertification landscape in some places.Rocky desertification is one of the main types of land desertification caused by water erosion.It takes place in the fragile karst geological environment.Under the influence of strong human social and economic activities,it is characterized by the degradation of land productivity and the appearance of a similar desert landscape.The fragile karst ecological environment forms surface and underground double-layer structure in southwest China accompanying with serious soil erosion.In addition,the carbonate rocks are interbedded with clastic rocks.In the topography,the landforms of the northeast towards ridges are parallel to the troughs.This special distribution of geomorphology blocks traffic,and the tunnel construction becomes the most convenient option to connect the mountainous areas.We put forward 3 scientific questions:Will a large number of tunnel constructions affect the soil and water loss on the surface?How does the rainfall condition affect the soil erosion of the karst trough?What is the impact of different land use methods on soil erosion in karst trough slopes?Based on the unique hydrological structure in the karst area,this paper uses the runoff plot method to monitor the process of runoff and sediment yield in the slope land,and uses the water chemistry method to quantitatively analyze the surface slope flow and the underground soil flow and the sediment carrying in the slope sand production.The main conclusions are as follows:1 The factors affecting the runoff coefficient are:rainfall>rainfall intensity;the factors affecting sediment yield are:high rainfall to the bottom:rainfall intensity?0.81?>rainfall?0.78?>runoff coefficient?0.53?;2 The runoff coefficients of the four runoff sites are from high to low:1#cultivated land?8.9%?>3#orchard?6.8%?>4#forest land?6.4%?>2#forest land?5.8%?;The erosion modulus values of the three runoff fields(high to low are:1#cultivated land?11.8t/km²/a?>3#orchard?7.5t/km²/a?>2#forest land?5.0t/km²/a?>4#???2.3t/km²/a?;4The 2#runoff field under the influence of the tunnel is larger than the 4#runoff field under the non-tunnel influence condition,and the ion loss?1383.7g?of the 2#forest land is larger than that of the 4#forest land?1292.7g?;The loss pathways of 5 K⁺and Na⁺ions are mainly slope flow.The loss pathways of Ca²⁺,Mg²⁺,Si⁴⁺and Al³⁺ions are mainly infiltration soil flow,and Si⁴⁺and Al³⁺ions are strongly affected by leaching,and the performance is obviously rich at the bottom.Collective.