小流域土壤水分空间异质性及其与环境因子的关系

以丹江口库区五龙池小流域为研究区域,利用双向指示种法将观测期(2008年4-10月)划分为不同干湿时段;运用前向选择法和Monte Carlo检验法对显著影响不同时段土壤水分空间格局的环境因子进行筛选;利用冗余分析排序法分析不同时段土壤水分格局与环境因子的关系;运用偏冗余分析定量分离环境、空间及其交互作用对土壤水分变异的影响.结果表明:观测期土壤水分被划分为7个子类,分别属于干旱、半干旱、半湿润和湿润4个时段;在干旱期,土地利用类型是影响土壤水分空间格局的主控因子,土层厚度、相对高程、剖面曲率、土壤容重和土壤有机质的影响也达到显著水平;在半干旱期,土层厚度起主导作用,土地利用类型、地形湿度指数、土壤容重和剖面曲率显著影响土壤水分;在半湿润期,地形湿度指数的影响最大,土地利用、坡向正弦值的作用显著;在湿润期,地形湿度指数和坡向正弦值是主要影响因子,相对高程、汇水面积的影响显著.不同干湿期土壤水分的空间分布与环境空间的生态梯度格局吻合较好.从干旱期到湿润期,环境因子独立作用不断减小,但始终处于主导地位,空间位置独立作用总体变化不大且一直维持在较低水平,环境-空间位置交互作用的贡献逐渐增大.

Spatial heterogeneity of soil moisture and its relationships with environmental factors at small catchment level

Taking the Wulongchi catchment of Danjiangkou in central China as a case, the soil moisture regime in the observation period from April to October, 2008 was divided into different dry-wet time periods by two way indicator species analysis (TWINSPAN), and the environmental factors that had significant effects on the spatial pattern of soil moisture in different dry-wet time periods were selected by forward selection and Monte Carlo tests. The redundancy analysis (RDA) was adopted to identify the relationships between the distribution pattern of soil moisture and the environmental factors in different time periods, and the partial RDA was applied to quantitatively analyze the effects of environmental factors, spatial variables, and their interactions on the variation pattern of the soil moisture. The soil moisture regime in the observation period was divided into 7 types, and grouped into 4 time periods, i. e. , dry, semi-arid, semi-humid, and humid. In dry period, land use type was the dominant factor affecting the spatial pattern of soil moisture, and the soil thickness, relative elevation, profile curvature, soil bulk density, and soil organic matter content also had significant effects. In semi-arid period, soil thickness played dominant role, and land use type, topographic wetness index, soil bulk density, and profile curvature had significant effects. In semi-humid period, topographic wetness index was the most important affecting factor, and the land use type and the sine value of aspect played significant roles. In humid period, the topographic compound index and the sine value of aspect were the dominant factors, whereas the relative elevation and catchment area were the important factors. In the four time periods, there was a better consistency between the spatial distribution pattern of soil moisture and the environmental ecological gradient. From dry period to humid period, the independent effects of environmental factors on soil moisture pattern decreased but were still in dominant, the independent effects of spatial location had less change and maintained at lower level, while the interactions between environmental factors and spatial location contributed more and more.