典型岩溶峰丛洼地坡面土壤水分空间变异性

Spatial variability of soil moisture on hillslope in typical karst peak-cluster depression areas

采用网格法测量典型坡面上旱季(12月)和雨季(5月)的表层(0～5cm)土壤含水量,以地统计学方法分析其空间变异性,结果表明:(1)与单一土地利用坡面相比,人为扰动强、土地利用多样的岩溶峰丛坡地表层土壤含水量表现为坡上未被扰动的自然植被区明显高于坡下人为改造的区域;旱季时坡地林地表层土壤平均含水量(32.8%)明显高于位于坡下的梯田空闲地(24.2%)、梯田橘园(20.0%)、梯田菜园(22.0%)、坡地裸地(23.5%);雨季时,坡地裸地(30.2%)和梯田橘园(32.1%)有明显增大,梯田空闲地(17.8%)剧烈减小,坡地林地(32.2%)土壤含水量依然最高;(2)旱、雨季整个坡面上空间结构比分别为21.0%、8.7%,表现为雨季的空间相关性更好;旱、雨季表层土壤含水量变异系数分别为20.1%和31.7%,属中等程度变异;雨季表层土壤含水量的变程(77.5m)显著高于旱季(8.0m),雨季的土壤含水量具有较好的空间变异结构;(3)裸岩周围空间的土壤含水量随与裸岩的距离增大而减小,梯田石坎周围空间的土壤含水量随与梯田石坎的距离增大而递减。

The study area is located in Guilin,Guangxi,with a land area of approximately 3,000 m^2.The area is characterized by humid subtropical monsoonal climate,with the average annual temperature 18.7℃and the average annual rainfall of 1,785.2 mm;and it＇s rainy season is generally from April to September,which belongs to the typical karst peak-cluster depression landforms.The study area include the hillslopes and the below terraces,and the terraces were previously transformed from hillslopes and used by villagers for the orangery and vegetable gardens.The exposed rate of rock in the middle of the hillslopes is more than 70%;and a large amount of exposed rock divide their soil into patches in the form of ＂rock gap soil＂ and ＂stone bowl soil＂ while retaining the upper native shrub.In order to reveal the spatial variability characteristics of surface soil moisture in typical karst peak-cluster depression hillslopes with strong artificial disturbance and land use diversity,selecting the slopes of the typical peak-cluster depressions and using grid method to measure the soil moisture content in the dry season（December）and the rainy season（May）,the spatial variability of soil moisture on hillslopes was analyzed by geostatistics.The results show that,（1）Compared with the slope of single land use,the surface soil moisture of the typical peak-cluster hillslopes is that undisturbed natural vegetation area located above the slope is significantly higher than artificial transformation of the region located below the slope,soil water content of sloping woodland（32.8%）that locating on top of the slope and undisturbed was significantly higher than terraced fields（24.2%）,terraced orange garden（20.0%）,terraced vegetable garden（22.0%）and bare land（23.5%）during the dry season.In rainy season,bare land（30.2%）and terraced origin garden（32.1%）had increased obviously and the terraced fields were drastically reduced（17.8%）,while sloping woodland（32.2%）remained the highest;（2）The spatial structure ratio is 21.0% and 8.7% during the dry and rainy season,respectively,indicating that the spatial correlation of the rainy season is better;the coefficient of variation of the surface soil moisture was 20.1% and 31.7% during dry season and rainy season,which are both belonging to moderate spatial variability;the range of surface soil moisture during the rainy season（77.5 m）was significantly higher than that of dry season（8.0 m）,which can be seen that the spatial variation structure of rainy season is better;（3）The change of soil moisture in the surrounding space of bare stone decreases with the increase of distance;soil moisture in the surrounding space of terrace bank is decreasing with increasing distance.