赣南地区侵蚀地形因子研究

Effects of topographic factors on soil erosion in Southern Jiangxi

【目的】研究南方红壤区水土流失非常严重地区的土壤侵蚀地形因子,旨在为水土流失治理提供参考。【方法】以赣南地区为典型样区,将该地区1∶10万图幅及其周边的16个1∶5万图幅拼接,然后用1∶10万图幅向外扩展5km后重新切割的范围作为数据处理的单元,基于Hc-DEM提取地形因子,用50m×50m的邻域窗口对坡度进行均值滤波,将赣南地区划分为平原(包括盆地及周边缓坡丘陵)、典型丘陵、山地3种地貌类型区,对这3种地貌类型区的坡度、坡长、坡度-坡长因子(Length-Slope factor,LS)的宏观和微观格局进行分析,研究地形因子与土壤侵蚀的关系。【结果】在宏观尺度上,平原的坡度和LS因子均最小,典型丘陵次之,山地最大;平原和典型丘陵区坡长较小,而在山地较大。在微观格局上,坡度表现出与地形连续变化相适应的特性;坡长在典型丘陵和山地反映出与提取算法有关的、类似流域单元的图式;LS受坡度和坡长的共同影响,整体上与坡度的分布一致。地形因子与土壤侵蚀的关系表现为,随着侵蚀强度的增加,坡度、坡长和LS因子均呈增加趋势。【结论】在南方红壤区水土流失非常严重地区,地形属性(坡度、坡长)和LS对土壤侵蚀影响明显。

[Objective] Effects of topographic factors on soil erosion in southern red soil region with se- rious soil and water loss problem were studied. [Method] Southern Jiangxi was taken as the typical sample area. Topographic factors were extracted from the recut map dataset with a 5 km extension of obtained 1 ： 100 000 map by merging 1 ： 100 000 sheet map of this region with 16 1 ： 50 000 maps of surrounding are- as. Based on Hc-DEM and a slope median filtration with 50 m × 50 m neighborhood window, the Southern Jiangxi region was categorized to three geomorphic types： plains （including basins and surrounding hills with gentle slope）, typical hills and mountains. Based on macroscopic and microscopic analysis of slope structure, slope length and Length-Slope factor （LS） of different landform types, the effects of topographic factors on soil erosion were investigated. [Result] On the macroscopic scale, mountains had the largest slope and LS factor, followed by typical hills and plains. Mountains had larger slope lengths than both plains and typical hills. On the microscopic scale, slope continuously changed as the terrain features. The slope lengths of hills and mountains showed similar watershed unit related to the extraction algorithm. LS factor was influenced by both slope and slope length, and was consistent with the distribution of the slope.Slope length and I.S factor increased as the increase of erosion intensity. [Conclusion] Topographic factors including slope, slope length and I.S had significant effects on soil erosion in red soil region.