蒙自喀斯特断陷盆地边坡与盆缘的露石差异性

喀斯特露石常常占据一定比例的地表面积,且具有许多已知或未知的水文—生态功能,对于喀斯特地区的植被恢复和环境改善发挥着重要的作用。本实验运用样线法和拍照法识别喀斯特断陷盆地不同位置(盆缘和盆地边坡)露石的数量特征和外部形态特征,同时比较了两种方法测量样地岩石裸露率的精准度。结果发现:盆地边坡与盆缘的露石数量和外部特征存在显著差异,盆缘露石分布密度(0.54个·m-2)>盆地边坡(0.39个·m-2);但盆地边坡露石的长宽比大于盆缘,单体占地面积为盆缘露石的两倍,接近40%的盆地边坡露石与山体等高线平行。样线法和拍照法测量样地岩石裸露率的结果存有差异,但并不显著,且这种差异呈现出随着岩石裸露率的增加而逐渐增加的趋势,拍照测量结果具有较小的变异系数。这些结果说明了研究区露石具有较强的空间异质性,对解释地表水土运移规律和植物分布提供重要参考。拍照法能准确地测量岩石裸露率,并提供露石外部形态特征的精准数据,可以作为喀斯特样地露石调查的新方法加以推广。

Differences Between Slope and Margin Rock Outcrop Characteristics in the Karst Fault-Depression Basin in Mengzi,China

Karst is a widely distributed geological landscape type in the world,accounting for about 12%~15%of the global land area.Rock outcrops are a common feature of karst landscapes and they drive a number of key hydrologic and ecological functions,including vegetation restoration and environmental improvement;however,there are few studies of the surface distribution and spatial heterogeneity of these features in karst areas.Therefore,the distribution density and external morphological characteristics(length-to-width ratio,angle,and area)of rock outcrops in faulted basin slope(FBS)and fault basin margin(FBM)karst landscapethe in Mengzi,China,were quantified by lines-plot(spline)and photographic methods;also the measurement accuracy was compared by the two methods.The results showed that there were differences in the quantity and external characteristics of rock outcrops between FBS and FBM:distribution density of rock outcrops was greater in FBM(0.54 per sq m)than in FBS(0.39 per sq m),whereas in FBS,length-width ratio of rock outcrops was greater than in FBM and area of single outcrops was twice as large than in FBM.Nearly 40%of rock outcrops in FBS ran parallel to mountain contour lines.There were no differences in measurements made by spline and photographic methods and the photographic measurements had smaller coefficient of variation.The result of both methods indicated spatial heterogeneity of the rock outcrops in the study area.There was evidence that any slight and non-significant differences between the measurement methods may increase with greater rates of rock exposure.The photographic method,which accurately measured rock exposure rate and external morphological characteristics of exposed rock,may be promoted as a new method for the measurement of rock outcrops in karst landscapes,and it may be used to provide reference material for the interpretation of theoretical soil and water migration dynamics and associated plant distribution.