黄土高原面积-高程分析及其侵蚀地貌学意义

Hypsometric Integral Analysis and Its Sediment Yield Implications in the Loess Plateau,China

黄土高原是中国乃至世界最为著名的水土流失区之一,黄河的泥沙主要来源于此。面积-高程积分(Hypsometric integral,HI)分析常被用于侵蚀地貌区的地貌发育阶段判定。通过探讨HI与DEM分辨率、分析窗口之间的尺度效应,分析了黄土高原HI空间格局和发育阶段性,并在此基础上揭示了侵蚀产沙和地貌发育关系。研究表明:利用不同分辨率DEM计算的HI具有很好的稳定性,HI对DEM分辨率不具有依赖性;然而,利用不同分辨率的分析窗口所计算的黄土高原HI值,表现出随着分析窗口的增大,HI表现出按照乘幂函数关系下降的趋势。黄土高原HI具有显著的空间分异特征,即汾渭谷地、宁夏内蒙沿黄冲积平原等地堑凹陷区是HI低值区,而黄土丘陵沟壑区是HI的高值区;黄土高原丘陵沟壑区地貌发育处于幼年期、壮年期和老年期的面积分别占总面积的7.9%、83.4%和8.7%,整体来看处于地貌发育壮年期;黄土高原丘陵沟壑区侵蚀产沙强度和地貌发育过程关系密切,HI与输沙模数存在显著的正相关。当前,黄土高原强烈的侵蚀产沙是其地貌发育处于壮年期的自然表现,这将是一个非常漫长的自然过程。

Loess Plateau of China is one of the most famous water and soil loss regions in the world where a large part of sediment discharge in Yellow River originates. Hypsometry integral analysis has generally been used to infer the stage of geomorphic development. In this paper, an auto-obtained HI （Hypsometrie integral, HI） method was developed using AML language of ARC/INFO. The results show that comparisons of hypsometric integral calculated from different DEMs is shown to he robust against variations of their resolution. However, hypsometric integral appears to he dependent on observed widow＇ s area and its show an inverse correlation according to power function with windows area. The HI of Loess Plateau shows a notable spatial difference characteristic. The lower HI mainly occurs in the Fenwei aggraded valley plains, Ningxia and Inner Mongolia alluvial plains and the high HI values mainly appear in the hilly and gully area of Loess Plateau. According to Strahler （ 1952）, the hilly and gully area of Loess Plateau is only 7.9% in the youthful stage （HI 〉 0. 6）, 83.4% in the mature phase （0. 35 〈 HI 〈 0. 6） and 8.7% in monadnock phase （HI 〈 0. 35） by the mean HI of different spatial scales There is a significant correlation between HI and suspended sediment yield in hilly and gully area of Loess Plateau （ r^2 = 0. 4756, n = 29, p 〈0. 001 ）, which indicated that soil erosion and sediment yield in Loess Plateau are closely related to the landform evolution. At present, the serious soil erosion and sediment yield in Loess Plateau that is a natural behavior for its mature stage in landform evolution, and that will he a long process until the landforms develop into monadnock phase.