中国阿尔泰山流域侵蚀速率及其控制因素

Basin-wide erosion rate in Chinese Altai Mountains and its controlling factors

流域侵蚀速率的时空变化对于理解活动造山带的地貌演化具有重要意义。以阿尔泰山8个山地流域为研究对象,利用1964—2011年的水文数据,采用河流输沙量法估算了年代际山地流域侵蚀速率。首先确定悬移质、推移质和溶解质对河流输沙量的贡献,然后计算各流域的年代际侵蚀速率,并结合已有研究结果,探讨了阿尔泰山流域侵蚀速率的时空特征及其控制因素。结果表明:阿尔泰山8个山地流域的平均侵蚀速率为0.03 mm·a^(-1),其中乌伦古河山地流域侵蚀速率最小(0.01 mm·a^(-1)),额尔齐斯河支流克兰河山地流域侵蚀速率最大(0.05 mm·a^(-1))。进一步对侵蚀速率与气候、地形、岩性、构造和植被等因素进行相关分析,发现流域侵蚀速率与地形因子(流域面积、地形起伏度)和气候因子(径流深度、平均温度)的相关性较强,表明这些因素可能对阿尔泰山山地流域侵蚀起主要影响。与阿尔泰山百万年尺度的剥蚀速率(0.07~0.3 mm·a^(-1))相比,研究时段内的流域侵蚀速率偏低,这表明中亚地区晚新生代持续的干旱气候可能制约了阿尔泰山地表侵蚀。

The spatiotemporal patterns of catchment basin erosion rate is vital for understanding the geomorphic evolution of active orogenic belts.Based on the hydrological data from 1964 to 2011,decadal-scale erosion rates of eight rivers(Haba River,Burjin River,Kelan River,Zhuolut River,Kuyiltes River,Zingali River,Burgun River and Ulungu River)basins are estimated by river sediment transport method.The contributions of suspended load,bed load and solute load to river sediment transport are first determined,and then decadal-scale erosion rates are calculated for each analyzed catchment basin.Here,we focus on the decadal-scale catchment basin erosion rate and its controlling factors in the Altai Mountains.The results show that the average erosion rate of the eight basins is 0.03 mm·a^(-1),among which the minimum erosion rate of 0.01 mm·a^(-1) is in Ulungu River,and the maximum erosion rate of 0.05 mm·a^(-1) is in Klan River,a tributary of the Irtysh River.Furthermore,in order to explore the potential effects of climate,topography,lithology,tectonics and vegetation on catchment basin erosion,correlation analyses were conducted between these factors and the erosion rate.It is found that there is a strong correlation between erosion rate and topographic factors(basin area,slope,and basin relief)and climatic factors(runoff depth and mean temperature),which may indicate that these factors have a major impact on erosion in the Altai Mountains.Compared with the million-year scales erosion rate(0.07~0.3 mm·a^(-1))existed now,the low decadal-scale erosion rate could imply that the continuous arid climate since late Cenozoic limited the surface erosion process of the Altai Mountains.