基于多重分形的黄土高原不同地貌类型区沟沿线起伏特征研究

Study on the Characteristics of the Topographic Relief of Shoulder Line of Different Geomorphic Types in Loess Plateau Based on Multi-Fractal

黄土高原不同地貌类型区沟沿线地形起伏具有不同的特征,有必要从局部和整体两个视角对其进行量化分析。该文以沟沿线地形剖面为研究对象,采用多重分形方法对选取的黄土高原6个典型地貌样区沟沿线地形的起伏特征和变化趋势进行研究。结果表明,黄土高原6个典型地貌样区的沟沿线地形起伏在整个空间尺度均表现出标度不变性,呈现出完全不同的多重分形特征。进一步计算并对比6个样区的多重分形参数Δα和Δf(α),绥德样区的Δα(0.6479)最小、Δf(α)(0.4941)最大,表明绥德样区沟沿线全局地形起伏变化的奇异性最小,而局部地形以高值起伏为主;甘泉样区的Δα(0.8945)最大,其多重分形特征最强,沟沿线整体地形起伏变化的奇异性最大;淳化样区Δf(α)(-0.4881)最小,其沟沿线局部地形以低值起伏为主。多重分形谱参数可作为黄土高原不同地貌类型区沟沿线地形起伏变化特征描述和评价的综合定量指标,为分析黄土地貌地形变化特征提供了一种新途径。

Different characteristics of the topographic relief of shoulder lines are caused by different geomorphic types in Loess Plateau,which need to be quantitatively analyzed from both the local and the global scale.By taking the terrain profiles of shoul-der lines as researdi objects in this paper,the relief characteristics and trends of shoulder lines of the six typical different land-forms in the Loess Plateau were studied by mult-fractal methods.The results show that the topographic relief of the shoulder lines of those landforms in the Loess Plateau all show the scale invariance in the spatial scale,and present different mult-fractal features.Through further calculation and comparison of mult-fractal spectrum parameters and topographic features of six dif-ferent types of landforms,the mult-fractal parameter Aa in Suide sample area with the value of0.6479is the smallest in all sample areas,while the parameter$f(A)which equals0.4941is the largest in all areas.Also,the values of these parameters in-dicate that the singularity of global topographic relief variation of the shoulder lines in Suide area is the smallest,and local topo-graphic relief is mainly high value fluctuation.As for Ganquan sample area,the value of Aa which equals0.8945is the largest in all sample areas,and its mult-fractal feature is the strongest as well as the singularity of global topographic relief variation of the shoulder lines is the largest.In addition,the value of Af(a)in Chunhua area which equals-0.4881is the smallest in all sample areas,and the top^igraphic relief of local terrain is mainly low value fluctuation.This suggests that the multi-fractal spec-trum parameters can be used as a comprehensive quantitative index for description and evaluation of the Loess Plateau in differ-ent landforms along the shoulder lines.The result also provides a new way for the analysis on terrain variation characteristics and evolution trends of loess landforms.