| A large number of granite is distributed on the surface of Longling County,whose surface weathering is strong,corrosion resistance is poor,and the terrain is undulating,steep slope,abundant rainfall,soil erosion is extremely serious,which poses a great threat to the safety of food production and people’s life and property in Longling County.Based on the data of rainfall,soil data,digital elevation,land use and remote sensing images in Longling County,the temporal and spatial distribution characteristics of soil erosion factors were analyzed.Secondly,CSLE model was used to estimate the soil erosion modulus of Longling County and analyze the temporal and spatial distribution characteristics and influencing factors of soil erosion in Longling County.Finally,through indoor artificial simulated rainfall experiment,three-dimensional laser scanning technology(TLS)was used to monitor the change of soil erosion in a small range in the study area,and the best soil and water conservation measures under different slopes were obtained,which provided basic support and scientific basis for soil and water ecological governance in Longling County.The research results are as follows:(1)The temporal and spatial distribution characteristics of rainfall,rainfall erosivity,land use and vegetation coverage were analyzed.In terms of spatial distribution,the average annual rainfall and annual rainfall erosivity in the four periods of Longling County show a decreasing trend from west to East,and there is no significant downward trend with the increase of time;The land use types are mainly cultivated land,forest land and grassland.In terms of spatial distribution,it is mainly reflected in the mutual transfer among cultivated land,forest land and grassland.In terms of time change,with the passage of time,the area of cultivated land and grassland decreases gradually,the area of forest land and construction land increases gradually,and the area of water area does not change significantly;In terms of time variation,the average values of the four periods were 79.81%,81.16%,83.14%and 84.03%,respectively,showing a significant upward trend with the increase of time.(2)The temporal and spatial changes of soil erosion in the study area in the past15 years were analyzed.From 2005 to 2020,the average soil erosion modulus of Longling County decreased first and then increased with 2015 as the inflection point,from 36.45 t/(hm~2·a)in 2005 to 27.66 t/(hm~2·a)in 2020;In terms of spatial distribution,the distribution characteristics of soil erosion intensity grades in the study area in the four periods of 15 years are micro>mild>moderate>strong>extremely strong>intense.Among them,the areas of micro erosion and mild erosion are 1503.24 km~2,1692.32 km~2,1821.84 km~2 and 1756.11 km~2 respectively,which show a fluctuating upward trend on the whole,The moderate and above erosion areas are 1298.26 km~2,1109.18 km~2,979.66 km~2 and 1045.39 km~2 respectively,showing a fluctuating and decreasing trend on the whole.The slight and mild areas in each period far exceed the moderate and above erosion areas.This shows that the intensity of soil erosion in Longling County shows the characteristics of slight and mild erosion in the past 15years.Although soil erosion fluctuates,it shows a good development trend on the whole.(3)The distribution of soil erosion under different environmental factors in Longling County from 2005 to 2020 was analyzed.With the increase of elevation,the average erosion modulus and erosion amount increase first and then decrease,reaching the maximum in the elevation range of 1350-2150m;With the increase of slope,the average erosion modulus increases gradually,while the erosion amount increases first and then decreases.The average erosion modulus and soil amount reach the maximum in the range of 15°-35°;Compared with semi shady slope and shady slope,soil erosion on sunny slope and semi sunny slope is more serious;Soil erosion mainly occurs in areas with vegetation coverage of 60%-80%and>80%;With the different land use types,the average erosion modulus and amount of Longling County are also different,and the decreasing order is cultivated land>grassland>forest land.(4)It is verified that the main factors affecting soil erosion are slope,vegetation coverage and soil and water conservation measures by the combination of artificial rainfall simulation test and three-dimensional laser scanning technology;The sediment yield rate has a positive correlation with slope,and a negative correlation with vegetation coverage and soil and water conservation measures,that is,with the increase of slope and vegetation coverage,the sediment yield rate of bare slope is increasing and decreasing respectively.The more complex the soil and water conservation measures are,the lower the sediment yield rate of slope is;From 10°to 40°,the best sediment reduction benefits are engineering+tillage measure ET1(10°),plant measure PM2(20°)and engineering+tillage measure ET2(40°). |
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