| Yunnan is one of the provinces with the most severe soil erosion in southwest China.Its also the birthplace or land of important rivers such as Yangtze River,Pearl River,Yuanjiang-Red River,Lancang River,Nu River and Irrawaddy River.Severe soil erosion caused by regional ecological environment degradation,shortage of land resources,prominent contradictions between people and land and natural disasters,seriously restricting the sustainable development of social economy in Yunnan Province.Soil erasibility factor(K value)is an important index to calculate the soil erosion modulus,while the current study of K value in Yunnan Province is not enough,which seriously restricts the implementation of regional soil erosion prediction and soil and water conservation management project.Based on the second national soil census data,this study carried out field replenishment sampling and indoor test analysis of the main soil types in Yunnan Province,constructed and updated the soil property database,mapped the K-value spatial map of Yunnan Province,and analyzed the K value and environmental factors And the correlation between the key factors.The results are as follows:(1)The mean soil erodibility K values for the Yunnan province was calculated as 0.0065[t·hm2·h/(hm2·MJ mm)],and the range of soil erodibility K values is 0.0004?0.0169[t·hm2 h/(hm2 MJ·mm)].The validation results that reliability of the calculation results is higher that compared with results of testing.The spatial differentiation is characterized by the highest in the middle and the lowest in northwestern of Yunnan.The K values is gradually increasing trend from west to east with the increase in longitude.The highest erodibility K value is Purplish soils and the lowest is Alpine frozen desert soils of 19 soil types in Yunnan province,the K values are respectively 0.0125 and 0.0004[t·hm2·h/(hm2·MJ·mm)].The Red earths is most extensive distribution inYunnan,its K values is 0.0069[t hm2·h/(hm2·MJ mm)].K values show trends that Farmland>Grassland>Woodland in different land use.The highest K value appears between 2000-3000 meter and the overall value of K showed a downward trend with the increase in slope.(2)There was a significant positive correlation between K value with annual mean temperature and longitude,and had a significant negative correlation with six environmental factors that soil type,average annual rainfall,slope,land use,elevation and latitude.The single factor soil types can explain change of K value about 49.03%,followed by altitude and annual average temperature drop that explain change of K value is 2.46%and 2.28%.Redundancy analysis(RDA)results show taht soil types has the greatest explanation for K value,and indicating that soil type,altitude and years of annual average temperature were the main controlling factors affecting spatial differentiation of soil erodibility in Yunnan Province.The soil type is the result of the combination of climate,vegetation,topography,parent material,earthing time and elements factors,it including a variety of environmental impact factors.Therefore,it impact on soil erosibility is of the most importance.(3)The results of this study show that the effect of climate change on soil erodibility is obvious in the same types of between different land use,and the largest impact on agricultural land for the middle and south of Yunnan.The decrease in annual mean rainfall and the increase in annual mean temperatures may lead to an increase in soil erodibility,which may exacerbate the potential hazards of soil erosion.In this study,the K value database was constructed,and the spatial differences of K values were clarified by calculating the K value of soil types,and the key environmental factors were identified in Yunnan Province.The results can provide data support for the quantitative estimation of soil erosion modulus,and provide theoretical basis for soil and water conservation in Yunnan Province. |
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