小流域土层厚度对土壤水分时空格局的影响

Effects of soil thickness on spatiotemporal pattern of soil moisture in catchment level

以丹江口库区五龙池小流域为研究区,通过定点观测,探讨了土层厚度对土壤水分时空格局的影响.结果表明:土壤含水量在降雨后立即升高,随后逐渐降低,空间异质性则相反.不同土层厚度剖面含水量差异显著.其中,0～20cm厚度的土壤剖面含水量较低,与降雨有相似的变化趋势,季节变异大;中等厚度(20～40cm)的土壤水分受降雨特征影响,剖面含水量居中,季节变异中等;较大厚度(>40cm)的土壤的剖面含水量较高,季节变异小.土壤水分的剖面格局是降雨、蒸发蒸腾和渗漏综合作用的结果,半湿润期呈增长型,湿润期呈波动型,干旱期包括增长型和波动型.土壤剖面含水量与土层厚度呈显著正相关,相关系数在0.630～0.855.土层厚度与表层(0～15cm)土壤水分相关不显著,但与中下层(20～55cm)土壤水分显著相关.

Based on the fixed-spot observation, this paper analyzed the effects of soil thicknesses on the spatiotemporal pattern of soil moisture in the Wulongchi catchment of Danjiangkou, China. The soil moisture content increased soon after precipitation events, followed by a decline as the soil dried down, whilst its spatial heterogeneity exhibited an opposite pattern. The profile-averaged soil moisture content differed significantly with soil thickness. The soil with a thickness of 20 cm had lower profile-averaged moisture content whose variation trend was similar to that of precipitation and varied obviously among seasons; medium thickness （20-40 cm） soil had medium level of profile- averaged moisture content whose seasonal variation was moderately and affected by the characteristics of precipitation ; while the soil with a thicknesses of 〉 40 cm had higher profile-averaged moisture content whose seasonal variation was relatively small. The profile distribution pattern of soil moisture was determined by the integrated effects of precipitation, evapotranspiration, and leakage, exhibiting increasing-type at semi-humid stage, waving-type at humid stage, and both of the two types at arid stage. There was a significant positive correlation between profile-averaged soil moisture content and soil thickness, and the correlation coefficient was 0. 630-0. 855. The moisture content in 0-15 cm soil layer had less correlation with soil thickness, but the moisture content in 20 -55 cm soil layer was significantly correlated with soil thickness.