| Soil erosion is considered as a major environmental threat in terrestrial ecosystems,which can easily cause a series of ecological and environmental problems.In this study,based on the Revision of the universal soil loss equation(RUSLE),the soil erosion modulus of Yunnan province was calculated by combining the long-term series precipitation data,soil type attribute data,DEM data,multi-temporal remote sensing data and land use data.The soil erosion situation in Yunnan province from 1985 to 2020was evaluated by Geo-Information-Tupu.Factors such as precipitation,soil type,slope length,slope,vegetation coverage and land use type were selected to determine the driving factors and the risk range of each factor of soil erosion in Yunnan Province by using geodetector method.In terms of prediction,based on the CMIP6 model,five emission scenarios of BCC-CSM2,Can ESM5,CMCC-ESM2,MIROC6 and NORESM2-MM and three different emission scenarios of SSP1-2.6,SSP2-4.5 and SSP5-8.5 were screened,and the treatment method of multi-mode ensemble average was adopted.To predict the precipitation in Yunnan province from 2021 to 2050,and to predict the spatial distribution of soil erosion in Yunnan province with the help of Markov model.The main conclusions are as follows:The analysis of the temporal change of soil erosion shows that:in terms of time series,the annual average soil erosion in the whole province shows a fluctuating and decreasing trend.From 1985 to 2020,the annual average soil erosion is 1.098 billion tons,among which the average soil erosion in 1990 is the largest,reaching 1.7 billion tons,and The minimum,584 million tons,occurred in 2015.The average erosion amount changed the most in 2000 and 2020,with a change rate of 41.65%and 69.86%respectively.The SL 190-2007 was used to classify the soil erosion intensity in Yunnan province.Generally speaking,the area of slight soil erosion increased and that of severe soil erosion decreased in Yunnan province during the past 36 years.In each year,the largest area and the highest proportion of soil erosion are micro erosion,and the smallest area and proportion of soil erosion is severe erosion.The change of soil erosion is related to the heavy rain and soil and water conservation measures such as slope farmland management.The characteristics of soil erosion in Yunnan province during the study period were analyzed from the perspective of spatial distribution.From the perspective of topographic and geomorphic partition,the narrow belt between mountain valleys in northwest,central and southern Yunnan were suffered severe soil erosion from 1985 to2000,mainly due to the steep slope and wide distribution of steep slope cropland.From2000 to 2015,severe erosion occurred only in the northwestern edge of Yunnan province,the high and middle mountain areas with an altitude higher than 2000m in western Yunnan province,and the high and middle mountain areas in southern Yunnan Province,which had a great causal relationship with the pilot project of comprehensive control of soil erosion in slope cropland launched in 2010.Compared with 2015,the area of severe soil erosion in 2020 showed a trend of westward expansion,possibly because the spatial distribution of short-time heavy rainfall in Yunnan province increased from west to east in this period.Soil erosion grade change active,level change,level of stable area accounted for 68.5%,31.5%respectively,the change area is mainly in the micro switch between erosion and the erosion of the light,the vast majority of evolution type are reduced to micro,from the high intensity erosion degree of erosion,soil erosion indicates that at the study period the province situation has improved.Soil erosion is more serious in the Wumeng Mountain area;The degree of soil erosion is improving in the plain hills of southeast Yunnan and the eastern side of Ailao Mountain.Yunnan province is divided into six geomorphic units according to altitude,namely plain,hill,low mountain,low mountainous,high mountainous and high mountain.Factors such as precipitation,soil type,slope length,slope,vegetation coverage and land use type were selected to quantitatively explore the driving factors of soil erosion in each geomorphic unit by using geographic detector method.The results show that slope has the greatest explanatory power for soil erosion within each geomorphic unit in Yunnan Province.The results showed that the dominant interaction factors driving soil erosion were the combination of slope,vegetation coverage,soil type and precipitation,and the interaction of the two factors within each geomorphic unit could enhance the explanatory power of soil erosion.Risk detection results showed that there were differences in the factor risk range of each geomorphic region,but attention should be paid to the areas with slope>20°,NDVI value of 0.6～0.7,and precipitation of1200～1600mm,followed by the primitive soil,anthropic soil,slope length>43m,unused land,grassland.The spatial-temporal distribution of soil erosion in the future shows that:Under the CMIP6 multi-model ensemble average method,the precipitation of Yunnan Province in the future(2015-2050)shows a trend of fluctuation increase relative to the historical period(1985-2014)under the three scenarios of SSP1-2.6,SSP2-4.5 and SSP5-8.5.Under the SSP1-2.6 scenario,the fluctuation range and increment of precipitation in the future are the largest in Yunnan Province.In terms of future land use types,construction land to cultivated land,grassland to cultivated land,and cultivated land to construction land are the three largest types of land conversion areas in Yunnan province in the future,with conversion areas of 458.55km~2,42.41km~2 and 37.13km~2 respectively.Under future climate change scenarios,the transfer area of cultivated land will increase,but improper agricultural operations will likely increase the risk of soil erosion in Yunnan Province.The area subject to soil erosion in Yunnan province will increase under the three climate scenarios in the future,and the perennial average soil erosion modulus and total amount in Yunnan province will be the largest under the SSP1-2.6 low emission scenario.Under the three scenarios,strong soil erosion in Yunnan province is likely to occur in the middle of the 21st century.From the perspective of space,high intensity soil erosion will occur in the longitudinal valley of Gaoligong Mountains,Wuliang Mountains and Ailao Mountains in the northwest to southeast direction under three different scenarios in the future.In addition,there is a risk that the soil erosion level in Pu’er city will change from slight to severe under the future SSP5-8.5 high emission scenario.The stability of soil erosion grade under SSP1-2.6 scenario was higher than that under SSP2-4.5 scenario and SSP5-8.5 scenario.By comparing the changes of soil erosion levels under the three scenarios,it is found that with the increase of emission levels in the future,the risk of soil erosion intensification in Yunnan province will be increasing. |
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