黄土塬区不同土地利用方式土壤水分对降雨的响应研究

Response of Soil Water to Precipitation under Different Land Uses in the Loess Tableland Region

以黄土塬区王东沟小流域塬面为研究对象,结合野外样品采集和室内外化验分析,探究不同土地利用方式下土壤水分、土壤水氢氧稳定同位素对次降雨事件的时空响应变化规律,为黄土塬区农业生产格局优化、生态修复提供科技支撑。结果表明:(1)在次降雨事件(降雨量47.6 mm)发生前及发生后7天,荒草地、苹果地和玉米地在0~3 m范围内土壤平均含水量分别为16.13%±1.23%、16.01%±1.38%、16.53%±1.43%。土壤水分对本次降雨事件响应的最大深度由大到小依次是玉米地、苹果地和荒草地,前二者存在响应滞后现象。采用有序聚类分析将土壤水分纵向变化层次划分为土壤水分活跃带、弱活跃带、相对稳定带,荒草地各层次深度范围分别为0~0.2、0.2~0.4和0.4~3 m,苹果地和玉米地均为0~0.2、0.2~0.6和0.6~3 m。(2)0~3 m土层蓄水能力由大到小依次是荒草地、玉米地和苹果地;(3)本次降雨事件下,雨水δ2H、δ18O分别为-81.30‰、-11.12‰;降雨后土壤表层的入渗能力大小依次为苹果地>玉米地>荒草地。0~3 m土层范围内土壤水氢氧稳定同位素随深度变化均表现出“多峰”的变化趋势,3种土地利用方式下雨水入渗均呈现“活塞流”和“优先流”交替进行的过程。

The study is carried out on the loess surface of the Wangdonggou sub-basin in the loess tableland region,combining field sample collection and indoor and outdoor laboratory analysis to investigate the spatial and temporal response of soil moisture and soil water-hydrogen-oxygen stable isotopes to secondary rainfall events under different land use patterns,with the aim of identifying the mechanism of soil moisture infiltration and redistribution in the loess tableland region,and providing scientific and technological support for the optimization of agricultural production patterns and ecological restoration in the loess plateau region. The results show that(1) before and 7 days after the rainfall event(47.6 mm),the average soil moisture content in the range of 0~3 m is 16.13% ± 1.23%,16.01% ± 1.38% and 16.53% ±1.43% in the barren grass,apple and maize fields,respectively. The maximum depth of soil moisture response to this rainfall event is in the order of maize field,apple field and barren grass field,with the first two having a lag in response. Soil moisture is classified into active,weakly active and relatively stable zones by using ordered cluster analysis,with the depth ranges of 0~0.2,0.2~0.4 and 0.4~3 m in the barren grassland,and 0~0.2,0.2~0.6 and 0.6~3 m in the apple and maize fields respectively.(3)Under this rainfall event,the rainfall δ2 H andδ18 O are-81.30‰ and-11.12‰ respectively. The infiltration capacity of the soil surface layer after rainfall is in the order of apple field >maize field > maize field;the stable isotopes of soil water hydrogen and oxygen in the 0~3 m soil layer shows alternating processes of“piston flow”and“preferential flow”for rainwater infiltration.