长江三峡山地集水区土壤水分空间变异特征

Spatial Variation Characteristics of Soil Moisture in the Three Gorges Mountain Catchment Area of the Yangtze River

为阐明亚热带湿润气候区山地坡面土壤水分的时空变化及影响因素,以三峡库区针叶林覆盖的中山凹坡为研究对象,采用经典统计学和地统计学的方法,对2019—2020年5 m×5 m网格点监测的117个点位0—70 cm土层深度的土壤水分数据进行分析,研究了湿润和干旱条件下典型凹坡集水区内土壤含水量的统计学特征与环境因子的相关性,以及土壤含水量的空间变异特征。结果表明:(1)水平方向上,集水区内各层土壤水分均表现为中等变异(10%<CV<100%),随土层深度增加,变异系数先增大后减小。0—40 cm土壤水分呈强烈的空间相关性,40—70 cm呈中等的空间相关性。集水区土壤水分的变程为8.40~18.47 m;(2)垂直方向上,湿润和干旱时期土壤水分的剖面变化规律基本相同。土壤水分基台值在剖面上呈“倒S”型变化趋势,随土层深度先增加后减小再增加。湿润时期土壤水分变程随土层深度增加而增大,而干旱时期变程随土层深度增加呈现波动变化;(3)湿润时期集水区土壤水分比干旱时期变异程度更高,空间相关性更好,较深层(40—70 cm)比较浅层(0—40 cm)空间相关性更好。0—30 cm土壤水分受地形(坡度)影响较大,变化趋势不稳定,30—70 cm土层深度土壤机械组成(黏粒、粉粒、砂粒含量)的作用加强,变化趋势趋于稳定。研究结果可为亚热带湿润气候区山地坡面生态水文过程研究提供数据与理论参考。

In order to clarify the spatial and temporal variation and the influencing factors of soil moisture on mountain slopes in the humid subtropical climate zone,taking the mid-mountain concave slopes covered by coniferous forest in the Three Gorges reservoir area as the research object.The soil moisture data of 117 monitoring points at a depth of 0—70 cm in a 5-meter grid during 2019 to 2020 were analyzed by using classical statistics and geostatistics methods.And this study investigated the correlation between the statistical characteristics of soil moisture content and environmental factors and the spatial variability characteristics of soil moisture content in the catchment area of typical concave slopes under wet and dry conditions.The results showed that:(1)Soil moisture of all layers in the catchment area showed moderate variability(10%<CV<100%)in the horizontal direction,and the variation coefficient increased first and then decreased with the increasing soil depth.Soil moisture in 0—40 cm soil layer showed strong spatial correlation,and that in 40—70 cm soil layer showed moderate spatial correlation.The variation range of soil moisture in the catchment area was between 8.40 and 18.47 m.(2)In the vertical direction,the profile variation pattern of soil moisture during wet and dry periods were basically the same.Soil moisture basal values showed an“inverted S”type trend in the profile,first increasing,then decreasing,and then increasing with soil layer depth.The variation range of soil moisture increased with the increasing of soil layer depth in the wet period,while the variation range fluctuated with the increasing of soil layer depth in the dry period.(3)The soil moisture in the catchment area during the wet period had a higher degree of variability and better spatial correlation compared to the dry period,and the spatial correlation was better in the deeper layer(40—70 cm)than in the shallow layer(0—40 cm).Soil moisture at 0—30 cm was greatly affected by topography(slope)and the trend of change was unstable,while soil particle composition(sand,silt and clay content)at 30—70 cm depth was enhanced and the trend of change tended to be stable.The results could provide data and theoretical references for the study of ecohydrological processes on mountain slopes in the humid subtropical climate zone.