Estimation Of K Factor Value Of Erodibility In Typical Alpine And Extremely High Mountain Belts In Southeast Tibet

As global warming has become a hot topic,soil erosion has been paid more and more attention and become one of the problems of global ecological security.As an important ecological security barrier,soil erosion in southeast Tibet has gradually emerged under the background of climate warming.However,due to its special geographical location and difficult environmental conditions,the Qinghai-Tibet Plateau has few measured data related to soil erosion research.Therefore,this study adopts to study the typical alpine and extremely alpine soils in southeast Tibet,and selects the soils above 4300 altitude of Sejira Mountain,Mira Mountain and Demla Mountain.By combining field investigation with indoor physical and chemical analysis,soil bulk density,water content,porosity,organic matter and particle composition distribution characteristics of 38 sample plots in the region were analyzed.EPIC model,Shirazi model and Torri formula were used to estimate soil erodibility K value in the region.The single factor variance analysis was used to analyze the basic properties of soil at different elevations,and the uncertainty of three erodibility formulas was evaluated by the error analysis method.The correlation between basic properties of soil and K value was discussed by Pearson correlation analysis.In order to provide a certain data basis and theoretical basis for soil erosion in the southeast Tibet mountain top.The results show that:(1)The study area soil bulk density and soil density range of the average of 0.98g/cm3 to 1.28g/cm3,0.63g/cm3 to 1.01g/cm3,are presented along with the change of higher altitude,fluctuated down trend;The mean value of soil porosity ranges from 51.58% to 62.92%,which is positively correlated with altitude.The average soil moisture content varied from 29.42% to 62.26%,and showed an "M"-shaped trend with the increase of altitude.Soil organic carbon(SOC)range in 31.31g/kg-2to 75.47g/kg-2,embodied in milasan highest,color gerahs the mountains with Germany’s SOC were similar;The distribution of soil particle size is mainly silt and sand content,and the texture is mainly silty loam.The fractal dimension ranges from 2.7313 to 2.8964,and varies with altitude by 4600m>4400m>5000m>4500m>4300m>4700m>4800m>4900m.Correlation analysis shows that physical and chemical properties have different degrees of correlation,among which the effect of altitude on physical and chemical properties can not be ignored.(2)The KEPIC value of soil erodibility in the study area ranges from0.0286 to 0.0461,and the sample data basically conform to normal distribution,which is mainly affected by altitude,SBD and PT.The KShirazi value of soil erodibility ranges from 0.0480 to 0.0484,and the sample data basically conform to normal distribution,which is mainly affected by altitude.The KTorri value of soil erodibility ranges from 0.0012 to 0.0075,which is manifested as Sejira mountain >Mount Mira >Demla Mountain is mainly affected by SBD,SPD,PT and silty(SIL).(3)The calculation of corrodibility K value in the study area is more suitable for Shirazi model.The mean absolute error(MAE),mean relative error(MRE)and root mean square error(RMSE)of Shirazi model are close to 0,while the precision factor(Af)of Shirazi model is close to 1.(4)According to the research results of Sejira Mountain,the transformation equation between EPIC model and Shirazi model is KShirazi=0.0345 KEPIC +0.0469,Torri formula cannot be linearly converted from the other two models;According to the results of Mira Mountain study,the conversion equations of the three models are respectively KShirazi=0.0418 KEPIC +0.0466,KTorri =0.0397 KEPIC +4E-05,KTorri=0.9291KShirazi-0.0433;According to the results of Demla Mountain study,the mutual transformation equations of the three models are respectively KShirazi =0.0548 KEPIC +0.0461,KTorri =0.0461 KEPIC-1E-04,KTorri =0.7552KShirazi-0.0348.