黄土丘陵沟壑区沟道造地土壤水分时空变异特征

Spatial and temporal variations of soil moisture of gully cultivated land in the loess hilly and gully region

基于Van Genuchten模型测定土壤水动力学参数,采用定点监测方法,在沟道中不同位置以及对照坡面进行土壤水分观测,分析了延安市典型治沟造地项目沟道造地土壤水分的时空变异特征,阐明治沟造地工程对沟道土壤水分的影响。结果表明:(1)土壤水力学参数在沟道土层深度为40 cm附近发生了显著改变,0~40 cm土层土壤容重1.12~1.25 g·cm^(-3),导水率达到40 mm·min-1以上,入渗能力强,同时饱和含水率较大,40 cm以下土层土壤容重在1.5 g·cm^(-3)左右,导水率在1.25~1.41 mm·min-1之间,入渗速率明显减小;(2)沟道土壤水分显著大于对照坡面,其季节变化稍滞后于降水的季节变化,整个生长季在15.76%~21.91%间波动,高出对照坡面5%左右,垂直分布随土层深度的增加而增加,表层最低,为15.07%,160 cm土层最高,为22.84%,深层土壤含水量优势更加显著;沟道土壤水分变异系数在0.131~0.234之间,相比较坡面,沟道表层以下土壤水分存在较强的空间异质性,100 cm以下土层变异系数在0.2左右,土壤水分变化活跃;(3)沟口土壤含水量显著高于沟头,土层深度40 cm以下的土壤含水量长期达到甚至超过田间持水量。通过治沟造地工程水分综合调控体系,沟道能够为作物生长提供水分充足的生境条件,提高水资源利用效率的同时改善农业生态环境。

The characteristics of spatial and temporal variation of soil moisture in gully were discussed to provide scientific basis for the rational allocation,efficient utilization of water resources and agricultural management in the Loess Plateau.Soil hydrodynamic parameters were measured based on the Van Genuchten model.The fixed-point monitoring method for observing soil moisture at different positions in gully and on control slope was used to analyze the temporal and spatial variation characteristics of soil moisture in the gully control and land consolidation project in Yan’an City and clarify the impact of the project on the soil moisture in the gully.The results showed that:(1)The soil hydraulic parameters changed significantly at the depth of around 40 cm of gully.The soil bulk density of layer 0~40 cm in the gully was 1.12~1.25 g·cm^(-3),and the hydraulic conductivity was more than 40 mm·min-1,indicating the characteristics of stronger infiltration capacity and higher saturated moisture content.While the soil bulk density of layer below 40 cm was about 1.5 g·cm^(-3),the hydraulic conductivity was 1.25~1.41 mm·min-1,and the infiltration rate was significantly reduced.(2)The soil water content of the gully was significantly greater than that of the control slope.Its seasonal variation characteristics were slightly lagging behind the falling seasonal,and it was fluctuate from 15.76%to 21.91%and it was about 5%higher than control slope in the whole growing season.The vertical distribution increased with the increase of soil depth,the lowest was 15.07%in the surface layer and the highest was 22.84%in 160 cm.The advantage of deep soil water content was significant.The variation coefficient of soil moisture in gully was between 0.131 and 0.234.Compared with slopes,the soil moisture below the surface of gully had strong spatial heterogeneity and changed actively below 100 cm with the variation coefficient being about 0.2.(3)The soil water content of the exit of the gully was significantly higher than that of the head of the gully,and the soil water content below 40 cm at the entrance reached or even exceeded the field water capacity for a long time.Through the comprehensive water control system in gully control and land consolidation project,the gully cultivated land could provide sufficient water conditions for crop growth and improve utilization efficiency of water resources and at the same time,agricultural ecological environment.