| Loess Plateau is the cradle and birthplace of Chinese civilization,and is one of the most serious areas of soil and water loss in China.Since the implementation of the policy of returning farmland to forest,the land use types,vegetation cover and soil condition of loess Plateau have undergone great changes.Yanhe River Basin is located in the loess hilly-gully region with broken terrain and ravines.In order to explore the characteristics of temporal and spatial dynamic change of soil erosion in Yanhe River Basin from 2000 to 2020,MODIS data,digital elevation model,land use type,daily rainfall and other data were adopted,and GIS,RS,CSLE model and other technologies were comprehensively applied.The temporal and spatial dynamics of soil erosion in Yanhe basin from 2000 to 2020 were systematically studied,and the driving factors were analyzed,as well as the contribution rates of rainfall factors and vegetation cover to soil erosion in Yanhe Basin.The main conclusions are as follows:(1)The annual rainfall erosivity of Yanhe Basin ranges from 1407.56 to 1982.25MJ·mm·ha-1·h-1·a-1,with an average value of 1529.03MJ·mm·ha-1·h-1·a-1.The distribution of rainfall erosivity decreases from southeast to northwest.From 2000 to 2010,rainfall erosivity increased gradually,and the average annual rainfall erosivity was 1615.97MJ·mm·ha-1·h-1·a-1.From 2011 to 2020,the mean rainfall erosivity in the basin decreased from 1415.25 MJ·mm·ha-1·h-1·a-1 to 1028.88 MJ·mm·ha-1·h-1·a1,and the mean annual rainfall erosivity was 1436.33 MJ·mm·ha-1·h-1·a-1.(2)In 2000,the area of forestland was 4394.64km2,accounting for 56.88%of the total area of the basin.The coverage rate of forest and grassland was 71.76%.In 2010 and 2020,the land use structure will still be dominated by grassland.The change of land use in Yanhe River Basin from 2000 to 2010 was mainly from cropland to grassland,and from forest to water.From 2010 to 2020,the conversion of land use in the basin is mainly reflected in the conversion between cultivated land and forest land,grassland and cultivated land.At the same time,the average vegetation coverage in 2000,2010 and 2020 were 55.75%,35.65%and 36.70%,respectively.In the elevation range of 700-1000m and slope range of 20°～25°,vegetation growth was dominant on the southern slope.(3)In 2000,the soil erosion grade of Yanhe river basin was mainly mild erosion,accounting for 41.28%of the total area of the study area.The average erosion modulus in 2010 increased by 3637t·km-2·a-1 compared with 2000,and the soil erosion intensity in 2020 decreased compared with 2010.From 2000 to 2020,the average annual soil erosion intensity of Yanhe River Basin showed a decreasing trend,and the average soil erosion modulus of period Ⅰ to period Ⅱ decreased by 2291.83 t·km-2·a-1.The soil erosion intensity of period I was mainly intensified,mainly distributed in Jingbian county,Zhidan County,Ansai County and Yanchang County.The decrease of soil erosion intensity in period Ⅱ was mainly distributed in the northwest of the basin in Zhidan,Jingbian and Ansai counties.(4)The elevation zone of 1000-1500m and the steep slope above 15° are the main distribution zone of soil erosion in the basin,which is the key zone of soil erosion control in the future.On each slope,soil erosion on the eastern and western slopes was more serious than that on the northern and southern slopes.Under different land use types,the proportion of soil erosion area was different,and the proportion of grassland moderate erosion and above soil erosion level was the largest.In the study area,the proportion of micro-erosion area was the largest under low,medium and high vegetation coverage.According to the contribution rate formula,the contribution rates of vegetation factors and rainfall factors are both positive,which promotes the decrease of soil erosion intensity.Figure[28]table[20]reference[81]... |
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