| Soil erosion in karst areas often leads to soil loss,thinning of soil layers and environmental degradation.At present,a lot of related researches have been carried out on the karst soil erosion problems,but the research on the soil erosion sedimentation by the method of grain size analysis needs to be further deepened.Therefore,this paper selects the karst stone buds slop in the middle of the Yunnan Province as the research area.In 2010,three sample plots of different stone buds were established.The field experiment,observation and sampling,laboratory analysis and grain size parameter analysis were carried out.Based on the work,this paper studied and analyzed the grain composition,grain size parameter characteristics and related changes of karst soil erosion sediments from 2010 to 2018.Besides,the related environmental factors were systematically studied and analyzed,in order to discuss the influence of different exposed rate of stone buds.Based on these conclusions,the paper can provide a theoretical basis for preventing and controlling water erosion on karst slopes and improving soil structure on karst slopes.The main research conclusions are as follows:(1)Grain composition and grain size parameters of karst soil erosion sediments are different between different stones buds exposed rate sample plots.The grain composition of the sediments in the three sedimentary pools is similar,with the highest percentage of silt,followed by clay,the lowest of sand.The range of Mean and D50 is A(75%exposed rate of stone buds)>B(50%exposed rate of stone buds)>C(zero exposed rate of stone buds).The proportion of sediments mode in the A sedimentary pool is 1.92 times,?1.62 times that of the B and C sedimentary pools.From the sorting of the sediments,the sediments particles of the three different stones buds exposed rate sample plots all showed poor sorting characteristics.The sediments of the A and B sample plots exposed by the stone buds basically are coarse skewed and mesokurtic,meanwhile,the sediments of the C sample plot without exposed stone buds are symmetrical and platykurtic.Besides,the sediments shows good fractal characteristics,and the more stone buds in the sample plots,the larger the fractal dimension of sedimentary sediments.There is a positive correlation between the fractal dimension of sediments and the percentage of clay.And it was positively correlated with the standard deviation of the sample plots exposed by the stone buds.(2)The range of grain composition and grain size parameters of karst soil erosion sediments are different with different stones buds exposed rate sample plots.The sample plots none of stones buds is fluctuating but the overall trend is relatively stable.From 2010 to 2018,the percentage of sand in the A sedimentary pool(75%exposed rate of stone buds)showed a trend of slow decline,the percentage of silt increased slowly,and the percentage of clay fluctuated,but showed a relatively stable trend;the percentage of sand in the B(50%exposed rate of stone buds)sedimentary pool shows a downward trend as a whole.and the percentage of silt and clay is generally increasing;The percentage of sand?slit?clay in the C(zero exposed rate of stone buds)sedimentary pool is fluctuating but the overall trend is relatively stable.From 2010 to 2018,Mean and D50 of the sediments in the A(75%exposed rate of stone buds)and B(50%exposed rate of stone buds)sedimentary pools showed a downward trend,and the C(zero exposed rate of stone buds)sedimentary pools fluctuated,but the overall trend showed a relatively stable trend;Mode of the sediments in the A(75%exposed rate of stone buds)sedimentary pool showed a trend of slow decline,the B(50%exposed rate of stone buds)and C(zero exposed rate of stone buds)pools were fluctuating,but the overall trend was relatively stable.(3)Discussion of the related environmental factors revealed that the environment in which soil erosion sediments with water flow is relatively medium energy compared to the rivers.At this time,the sediments transporting method is mainly based on the saltation.And there is an unstable and relatively strong hydrodynamic environment.,at this time,the grain transport is in the way of bed load transport.(4)The study of typical plots of karst stone buds land shows that soil erosion and grain size change are mainly affected by the exposure rate,soil properties,rainfall and slope of the karst plots.Under the condition that the other relevant conditions are basically the same,the main factors causing the difference of sediment particle composition and grain size parameter characteristics of soil erosion in each plot should be related to the difference of stone buds exposure rate. |
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