中国水土流失土壤因子数学模型

The Mathematical Models on Soil Factor of Water and Soil Loss in China

通过对现有水土流失土壤指标的分析、筛选 ,确定一建模函数的主要变量 ,提出了“土壤指数”的概念并把其用作模型因变量 ;通过侵蚀过程分析和数理推导确定了模型的基本形式 ;用模型变量的野外和室内实测数据对概念模型进行了参数拟合 ,初步建立了我国水蚀区水土流失土壤因子数学模型Ⅰ和模型Ⅱ ;进而对模型的应用问题进行了讨论。

Quantitative study on soil factor of water erosion in macroscopic regions is generally done by establishing the mathematical models.In view of various shortages existing in quantiative moedls of soil factor developed.It is necessary to build up new nationwide matematical models of soil factor for the comparison of soil erodibility among the regions.Two problems of the establishment and application of Soil Index Models are discussed in the article. The steps of the models'establishment are as follows: 1. Determining the models'variables.The models'variables have been determined according to the soil indictors'properties.All of the indictors are generalized as three types:attributive indictors,designative indictors and synthetical indictor.Attributive indictors and designative indictors can merely be used as independent variables,while synthetical indictor as an dependent variables,so the concept of soil index 'S'is proposed and used as dependent variable of the establishing models.Two functions and their variables are determined by analysis and selection of soil indictors existed at present used in warter erosion,these are S=f(B,K j,r), S=f(x 1x 2x 3x 4x 5x 6x 7x 8) where S is soil index,B is soil collapse rate ,K j is soil anti-shearing intensity,r is soil steady filtration rate,x 1 to x 8 refers to mealy sand to clay ,capacity,specific gravity,water content,granule content of water stability,cation exchange amount,organic matter,effective root amount. 2. Calculating the concept model.Concept model is ascertained by analysis of the erosion process and mathematicsl calculations of suspension matters,run off,and so on .it is S=W-x·K j+b·BW·r where w,x,b and W are the parameters awaiting determination,S,K j,B and r are the same as mentioned above. 3. Estimating the parameters.According to the firsthand data obtained through field test and indoor analytic data of the physical and chemical properties of soil samples,parameters in the concept models are estimated,and the ModelⅠand model Ⅱof soil factor of water erosion in China have praliminarily been built: S=1.57-2.57K j+3.29r (R 2=0.712,a=0.05) S=258.8-(18/x 1-84.1x 1-2.6x 2 1)+(32.5x 2-6.2x 2 2)-(2.8x 3-0.9x 2 3) +(2.7/x 4+1.1x 4)+0.56x 5-(341.2x 6+211x 2 6)+17.6x 7-23.7x 8) (R 2=0.624,α=0.05) The application and revision of the models are discussed too.As to the models'application,Firstly,Soil Index Model,as one of the sub models,is mainly to meet the need of the development of Chief Estimation Model of Water Erosion in China.Secondly,Model Ⅰhas a higher accuracy for the prediction of soil losses and Model Ⅱis more convenient for application.Theirdly,soil erosion mechanism analysis ahas been taken much count of and the indicators selected in the models are more comprehensive than K factor in USLE or RUSLE.But it is necessary to reasonably modify or revise the concept models and their parameters with the more data obtained by field and indoor tests.