区域沙漠化研究中的沙漠化数量表征

在区域尺度的沙漠化研究中,沙漠化的数量表征可以从沙漠化程度和沙漠化过程二个方面来表示,沙漠化程度是区域内不同沙丘类型的加权作用的总和,用公式DG_i=(M_i+k₁SM_i+k₂F_i)/A_i来计算。沙漠化过程是描述沙漠化程度的变化速率,即单位时间内的沙漠化程度的变化速率,用公式DP=(DG_i+n-DG_i)/n来计算。其中权重k值的确定是区域沙漠化研究的核心,因为k值的大小影响到区域沙漠化程度的高低。研究的结果表明,k值与沙漠化程度呈正关联。但是,其引起的变化小于不同沙丘类型面积变化引起的沙漠化程度的变化。因为采用上述公式计算区域尺度上的沙漠化程度和过程,主要反映了不同沙丘类型的面积信息,权重k值仅仅是对其进行了校正。同时研究结果也表明,k值与沙漠化程度的关系为线性关系,对k值的异议引起的沙漠化程度和过程的差别,可通过k值曲线及时地纠正或重新计算。此外,在不同沙丘类型面积确定的情况下,用k值曲线可表示出所研究地区沙漠化程度和沙漠化过程的变化范围。

Quantitative Expression in Regional Desertification Study

In this paper we emphasized that desertification could be described in two items;these were desertification degree and desertification process.Among of these,the desertification degree has been defined as relative area of total weighted influence of different dune types in research region and expressed as DG_i=(M_i+k₁SM_i+k₂F_i)/A_i(where DG_i is the desertification degree;M_i,mobile dune area;SM_i,semi-fixed dune area;F_i,fixed dune area;k₁,k₂;weights.).Simultaneously,the desertification process defined the change ratio of the desertification degree in certain period and calculated by DP=(DG_i+n-DG_i)/n(where DP means the desertification process;DG_i+n and DG_i,the different temporal desertification degree.).How to make sure k value value significantly influenced the desertification degree.Results showed that the values were positively correlative with the desertification degree.Distinctively,the effects of changing scope which induced by the values was less than the change of areas of different dune types,because major aspect of the functions emphasized the information of different dune types areas in region scale.However,the values just modified the different dune types areas.Meantime,results also showed that relation between the values and the desertification was linear regression,the deviation of the desertification degree and process that induced by the values could be recalculated and modulated by using the k values curve.In addition,the values curve as well as expressed the changing scope of the desertification degree and process in study region under the different dune type areas were unchangeable.