四川大凉山典型小流域切沟空间分布特征与影响因子

Spatial distribution and impact factors of gullies in a typical small watershed of Daliangshan,Sichuan

为探究大凉山区切沟空间分布特征及其影响因子,选择孙水河上游典型小流域,综合采用遥感监测、实地调查、GIS统计与分析等手段,研究切沟形态特征及空间分布规律,并运用地理探测器探讨影响切沟空间分布的关键因子。结果表明:1)研究区内切沟数量多,分布广,主要集中在流域东南一带(上游),向西北一带(中下游)呈逐渐下降趋势;流域内最大切沟密度6.53 km/km^(2),侵蚀强度轻度以上区域面积103.38 km^(2),占流域总面积的58.12%。2)地层岩性、高程、土壤类型和土地利用方式是影响小流域切沟空间分布的关键因子,小流域海拔3020~3150 m、地层为小坝组或窝头山组、土壤类型为亚高山灌丛草甸土、土地利用方式为裸地或撂荒地的区域切沟分布较为集中。研究成果可为大凉山区水土保持措施的布局提供决策支撑,为当地生态文明建设以及农业生产发展提供科学依据。

[Background]As an important ecological security barrier area in the upper reaches of Yangtze River,the gully in Liangshan prefecture is widely distributed,which leads to a serious soil loss and the continuous increase of river sediment.The development of gully is a complex process under the interaction of multiple factors such as topography,geology,soil,and human activities.The Mibume small watershed was selected as the study area due to its severe gully development,critical topography and land use.The study aims to investigate the spatial distribution of gully and its key impact factors in this typical mountainous watershed.[Methods]Based on GF-2 image,remote sensing visual interpretation was selected for extracting basic information of gully.Then field survey,GIS statistics and analysis were combined to integrate gully information and study its spatial distribution.Geographical detector was selected to compute the key factors of gully distribution and its influencing effects.[Results]1)The gullies in this study area had a large number and a wide distribution.They were mainly concentrated in the southeast(upstream)area of this small watershed with a gradually decreasing trend towards the northwest(midstream and downstream).The highest density of gullies in this small watershed reached 6.53 km/km^(2).The area of gullies above moderate erosion intensity reached 103.38 km^(2),accounting for 58.12%of the total area of this watershed.2)Sorted by level of impact,the key factors influencing the spatial distribution of gullies were stratigraphic lithology,elevation,soil type and land use.The gullies were concentrated in the area with elevation of 3020-3150 m,stratigraphy of Xiaoba Group or Wutoushan Group,soil type of subalpine scrub meadow soil,and land use of bare land or abandoned farmland in the sub-basin.[Conclusions]The special impact factors(stratigraphic lithology,elevation,soil type and land use)of this small watershed led to a wide distribution and a large number of gullies,which were concentrated in higher altitude areas.The research results of this paper can promote the layout of soil erosion projects and the application of soil conservation measures in Daliangshan,besides it is also beneficial to the construction of local ecological civilization and the development of agricultural production.