基于微地形和土地覆被的土壤水分空间变异性——以玛纳斯河流域绿洲为例

Spatial Variability of Soil Moisture Content Based on Microrelief and Land Cover——A Case Study in Oasis in the Manas River Basin

采用经典统计学和地统计学方法,对玛纳斯河流域绿洲0～70 cm土层土壤水分的空间异质性及其影响因子进行研究。结果表明:各层土壤水分均符合正态分布。从变异系数看,均属于中等变异,变异系数介于0.293～0.371,其中表层水分变异程度最高,达到0.371;0～10 cm,10～20 cm,20～30 cm和30～50 cm的土壤水分半方差模型为指数模型,50～70 cm层为高斯模型,拟合效果均较好,但块金效应明显,受结构性和随机性因素的共同作用,具有中度相关性,各层的空间自相关距离在40.2～489 km。Kriging插值结果表明,各层土壤水分的分布格局相似,表现为条带状和斑块状分布,土壤水分的空间分布受地形和农业种植的影响较大。由相关分析可知,相对高程与土壤水分呈正相关,并对表层土壤水分影响显著。在不同坡度等级下,各层的土壤平均含水量随土壤深度增加而增加。通过比较农田与盐碱地的土壤水分变化,发现2种土地的土壤水分均表现出随土壤深度增长型。0～30cm层农田水分大于盐碱地,而30 cm以下则相反。

The aims of this study were to explore the spatial heterogeneity of soil moisture content at depth of 0-70 cm and its affecting factors in oasis in the Manas River Basin.The relations between soil moisture content and microrelief as well as land use types were analyzed using the methods of traditional statistics and geo-statistics.The results show that soil moisture content was in normal distribution and moderate variability in the study area.The coefficient of variation of soil moisture content varied in a range of 0.293-0.371,in which that of topsoil moisture content was the highest.According to the highest r2 values,the best simulation model of soil moisture content above 50 cm in depth was exponential model,Gaussian model was applicable for soil layer of 50-70 cm,but the nugget effect was significant due to the structural and random factors.The spatial autocorrelation distance of all soil layers varied in a range of 40.2-489 km.The values interpolated with Kriging interpolation reveal that the spatial distribution of soil moisture content of all layers was similar and in strip and patch distribution patterns.Pearson correlation analysis shows that soil moisture content was positively correlated with elevation,and elevation affected significantly topsoil moisture content.Slope affected soil moisture content variability.Soil moisture content at soil layer of 0-70 cm increased with the increase of soil depth under different slopes.Soil moisture content above 30 cm in depth in farmland was higher than that in saline or alkaline land.The study results are of significance in vegetation regeneration and ecological balance in arid regions.