| Soil erodibility reflects the degree of difficulty of soil dispersion and removal under the circumstances of raindrop splash and runoff erosion.Soil erodibility factor?K?is an important indicator of soil erodibility,which is not only a necessary parameter to evaluate the sensitivity of soil erosion and the prediction model of soil erosion but also a technical provider for regional soil and water monitoring.With Yi yuan county-a national key administration area of Yi meng Mountain as the research object,this paper,through field investigation,laboratory experiments and runoff plot observation,analyzes soil types,texture,particle fractal and organic matter and other factors that affect soil erodibility factor?K?.This paper adopts standard runoff plot method and mathematical formula?NOMO formula and EPIC equation?to calculate K value,estable lishes linear regression equation between standard runoff plot measure value and mathematical formula method value and obtains repaired NOMO formula K value.Based on the repaired NOMO formula,this paper obtains spatial distribution of Yi yuan county's K value by the using geostatistics variogram and ordinary kriging to execute spatial interpolation.The main conclusions are as follows:?1?The main factors affecting soil erodibility factor?K?are analyzedThe county boasts a total of 1635.80 km2 soil area,most of which are brown soil and cinnamon soil.Brown soil has an area of 717.85 km2,accounting for 43.88 %.They are mainly distributed in granite area.Cinnamon soil has an area of 886.87 km2,accounting for 54.22 %.They are mainly distributed along the limestone area of Yi River.The soil has a coarse texture,most of which are sand and loam.The sand area is 649.22 km2,accounting for 39.69 %;it distributes in Da Zhuang Town and Southern Lu shan Mountain.Moreover,it is characterized by poor soil,and has no fertilizer and no water conservation.The loam area has an area of 338.13 km2,accounting for 20.67 %.It mainly distributes along the river and has good cultivation and fertility.The soil particles are mainly sand and silt,respectively accounting for 52.28 % and 41.26 % and they have a medium intensity variation.The distribution of soil particle fractal dimension ranges from 1.9729 to 2.7706,the average is 2.6034,and the variation coefficient is 5.50 %,belonging to the weak variation.The average content of soil organic matter is 18.19 g/Kg,maximum value is 37.66 g/Kg,minimum value is 5.95 g/Kg,amplitude range is 31.71 g/Kg,and variation coefficient is 35.13 %,belonging to medium intensity variation.Organic matter content in different soil types is Cinnamon soil> brown soil > leached cinnamon soil > minimal curve scoliosis > brown earth soil > cinnamon soil > fluvo aquic brown soil > Alluvial soil.The content of organic matter in different land use is Grassland > shrub land > woodland > orchard > Dryland,belonging to medium intensity variation.?2?Soil erodibility factor?K?is calculated and repairedThe soil genus K values is calculated through standard runoff plot method are as followed: Acid and brown soil is 0.019 in Xin Zhuang,Lin qu.Calcareous cinnamon soil is 0.028 in Qian Cheng zi,Meng yin.Mafic brown soil is 0.037 in Yao xiang Tai an.NOMO formula estimating soil genus K value are as followed: acid and brown soil is 0.018,calcareous cinnamon soil is 0.025,mafic brown soil is 0.036.EPIC equation estimating soil genus K value are as followed: acid and brown soil is 0.028,calcareous cinnamon soil is 0.031,mafic brown soil is 0.047.The standard runoff plots of repaired NOMO formula and EPIC equation are calculated by adopting standard runoff plot method to calculate the K value and using the estimated K value through mathematical formula to analyze linear regression.By adopting error analysis method to determine the repaired NOMO formula is more suitable for Yi yuan County for K prediction.Standard runoff plots repaired EPIC equation:Standard runoff plots repaired NOMO formula:K=0.9838×[2.1×10-4M1.14?12-OM?+3.25?S-2?+2.5?P-3?]/100+0.0021?3?Yi yuan County of soil erodibility factor K value is estimated and spatial interpolation is completedAccording to the repaired NOMO formula,the average K value of Yi yuan County is estimated to be 0.0308,the minimum value 0.0032,maximum value 0.0969,amplitude range 0.0937,and the Variation coefficient 57.47 %,belonging to medium intensity variation.The K value has a significant negative correlation with sand content,positive correlation with silt content,clay content and fractal dimension,no significant correlation with organic matter content.The higher the content of sand,the smaller the fractal dimension.The higher the content of powder and clay,the greater the fractal dimension and so is the K value.This paper uses variogram and ordinary kriging in geostatistics to calculate the spatial interpolation of K values,and the average K value is 0.0389.The soil types of K values are brown soil?0.0313?,cinnamon soil?0.0423?,fluvo aquic soil?0.0477?and bare rock?0.0284?.The sub types of average k value is between 0.0283 and 0.0478,among which leached cinnamon soil?0.0478?and fluvo aquic soil?0.477?have a higher K value and brown soil?0.0283?and bare rock?0.0284?have a lower K value.The county's K value is generally high in the middle and both sides decline in strip distribution.The spatial variability of K value is mainly caused by soil type,parent material,topography,organic matter content and other factors,the utilization of soil can also affect the spatial variation of K value.The high soil K value is mainly distributed in the hilly and low mountain landform types,where human activities are frequent,silty loam and soil are main texture,land use is mainly based on the drought terrace and orchard,the organic matter content is not high,the fractal dimension is large,the K value is high and the corrosion resistance is weak.The low soil K value was mainly distributed in low mountain landform types,the soil types are mainly brown soil,the texture is mainly sandy soil and sandy loam,the distribution of organic matter is uneven,the fractal dimension is small,the K value is low and the corrosion resistance is strong. |
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