| Soil erosion is one of the major global environmental problems,which has a serious restrictive effect on the existence and development of human society and the sustainable development of social economy in the world.Prevention and control of soil erosion,optimization of ecological environment and construction of livable environment are widely concerned by people from all walks of life in the world.Central Yunnan Province is composed of 42 counties and municipalities in Kunming,Yuxi,Qujing and Chuxiong.It is rich in natural resources and has a high level of social and economic development.It is the political,economic,cultural and transportation center of Yunnan Province.However,with the continuous progress of modernization,the urban area in Central Yunnan Province has been expanding,the original natural environment has been destroyed,and the ecological environment in the region has become more and more fragile.To clarify the temporal and spatial changes of soil erosion can provide a basis for ecological security maintenance and ecological construction.With multi-period remote sensing images as data sources and with the support of GIS technology,RUSLE model was used to evaluate the soil erosion grades of Central Yunnan Province in 1980,1995,2000,2005,2010,2015 and2018.The temporal and spatial variation of soil erosion grades was analyzed,and the relationship between natural environmental factors and spatial distribution of soil erosion intensity was explored.The main research contents and conclusions are as follows:1.The calculation method of soil erosion factors in the study area was selected.Combining with the actual situation of the study area,the factor calculation method proposed by domestic and foreign scholars is comprehensively analyzed,and the best algorithm suitable for Central Yunnan Province is selected.Rainfall erodibility R factor is calculated by a general simple algorithm.Soil erodibility K factor is solved by EPIC model.Slope S factor is calculated by considering the influence of gentle and steep slopes,and soil and water conservation measure P factor is obtained by assignment.Slope length L and vegetation coverage C factor are calculated by conventional algorithm.2.The temporal variation of soil erosion in Central Yunnan Provinc during 38years was analyzed.From 1980 to 2018,the area of moderate and above soil erosion in Central Yunnan Provinc showed a trend of increasing first,then decreasing,and just like inverted"U"type.Corresponding areas of erosion were 12899.06 km~2,14789.11km~2,20005.06 km~2,23144.97 km~2,20154.79 km~2,19962.68 km~2 and 12381.04 km~2,respectively.Among them,the area of moderate and above erosion increased year by year before 2005,with an increase of 10245.91 km~2 in 25 years,accounting for10.84%of the total area of the region;after that,the erosion area decreased year by year,and the range of change also reached 10763.93 km~2,accounting for 11.38%of the total area of the region.The change of annual average soil erosion modulus is consistent with that of moderate and above soil erosion area.Taking 2005 as a turning point,the change of modulus increases first and then decreases,from 1354.95t/(km~2·a)in 1980 to 1000.25 t/(km~2·a)in 2018.The results show that there are fluctuations in soil erosion in Central Yunnan Provinc during the past 38 years,but the overall trend is to reduce the degree of soil erosion.3.The spatial distribution of soil erosion in Central Yunnan Provinc during 38years was analyzed.There are more flat land in the central and eastern part of Central Yunnan Provinc,and most of the soil erosion is slight and mild,while the extreme intensity and severe erosion are mainly distributed in the mountains and valleys in the north and southwest of Central Yunnan Provinc.The spatial distribution of soil erosion intensity is significantly correlated with the topography of the region.Through the global spatial autocorrelation,it is concluded that the spatial distribution of soil erosion intensity in Central Yunnan Provinc has significant aggregation,and the global Moran I index is between 0.48 and 0.66,which indicates that the spatial distribution regularity of each intensity grade is obvious.Through the analysis of local spatial autocorrelation,it is found that most of the moderate and above intensities are concentrated in the alpine valleys of the region,which further proves that the distribution of intensive soil erosion is mostly related to the regional topography and topography.4.The relationship between regional soil erosion intensity and natural environmental factors was studied.With the help of Geodetector,it was found that elevation,slope,vegetation coverage and annual rainfall all had significant effects on spatial distribution of soil erosion intensity,among which vegetation coverage had the most significant effect,and its q value was above 0.28.In the factor combination,the q value of vegetation coverage and slope is between 0.51 and 0.68,which reflects that the spatial distribution of soil erosion intensity is highly correlated with vegetation coverage and slope.From 1980 to 2018,the overall development of soil erosion in Central Yunnan Provinc was good,the spatial distribution characteristics of soil erosion intensity were proved,and the relationship between intensity distribution and natural environmental factors had been preliminarily studied.However,more in-depth exploration and research were needed to improve the accuracy of soil erosion estimation and the relationship between natural environmental factors.In the monitoring and control of soil erosion,the factors of slope and vegetation coverage in the region should be paid more attention,and the alpine and valley areas should be taken as the key control points. |
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