黄土区水土保持林地的蓄水动态及雨水渗透深度

Water storage dynamics and infiltration depth of soil and water conservation forest in the Loess Plateau of western Shanxi province

为探讨黄土高原水土保持林地蓄水动态特征,分析水土保持林在造林时修建的水平阶成林后对雨水及径流的再分配效果,以及不同降雨条件下雨水的渗透深度,以晋西黄土区典型的人工水土保持林地侧柏(Platycladus orientalis)林地和油松(Pinus tabuliformis)林地为对象,利用Enviro SMART土壤水分定位监测系统,于2016全年在林地坡面和水平阶上以30 min 1次的频度测定0～200 cm土层的含水量,利用长期自记雨量计测定林外降水量,根据水量平衡原理分析水土保持林地蓄水量的动态变化特征、林地水分的积累速率和消退速率,根据湿润锋探讨降水量对雨水渗透深度的影响。研究结果表明:1)侧柏林地和油松林地200 cm土层的平均蓄水量分别为368. 99 mm和320. 58 mm。2)水平阶的平均蓄水量(408. 55 mm)>坡面的平均蓄水量(281. 01 mm),水平阶较坡面多蓄水127. 54mm。3)根据变异系数,水土保持林地蓄水量的年内变化可划分为稳定期(2—4月)、积累期(5—7月)、波动期(8—10月)、消退期(11—翌年1月)。4)积累期蓄水量的平均积累速度分别为:侧柏林地0. 68 mm/d,油松林地0. 64 mm/d;消退期蓄水量的平均消退速度分别为:侧柏林地0. 34 mm/d,油松林地0. 36 mm/d。5)侧柏林地雨水的渗透深度大于油松林地,水平阶上的雨水渗透深度大于坡面。暴雨条件下侧柏林地雨水的入渗深度为90 cm(坡面)～110 cm(水平阶),油松林地为60 cm(坡面)～70 cm(水平阶)。

[Background]In order to explore the dynamic characteristics of water storage in the soil and water conservation forests on the Loess Plateau,the redistribution effects of the level terraces on rainwater and runoff,and the depth of rainwater penetration under different rainfall conditions were analyzed.[Methods]In this study,artificial Platycladus orientalis forest and artificial Pinus tabuliformis forest in the Loess Plateau of western Shanxi province were selected as research objects,the soil moisture content of 0-200 cm soil profile and the precipitation were determined respectively,through the application of EnviroSMART soil moisture monitoring system and HOBO tipping rain gauge.Based on the theory of water balance,the dynamic characteristics of forestland water storage capacity,the rate of forestland water accumulation and the rate of extinction were analyzed,and the effect of precipitation on the depth of rainwater penetration was explored based on the wetting front.[Results]1)The soil water storage of P.orientalis forest(368.99 mm)was greater than that of P.tabuliformis forest(320.58 mm).2)The average annual storage water of the level terrace(408.55 mm)>the average annual storage water of the slope(281.01 mm),On the level terraces,the storage is 127.54 mm more on the slope.3)According to the coefficient of variation of soil water storage capacity,a year could be divided into 4 periods,stabile period of soil moisture(February-April),accumulation period of soil moisture(May-July),fluctuation period of soil moisture(August-October),fading period of soil moisture(November-January of the next year).4)The average accumulation rate of water storage during the accumulation period is 0.68 mm/d in the P.orientalis forest,0.64 mm/d in the P.tabuliformis forest,and the average speed of the water in the fading period is 0.34 mm/d in the P.orientalis forest,0.36 mm/d in the P.tabuliformis forest.5)The penetration depth of the rainwater in the P.orientalis forest is greater than that in the P.tabuliformis forest.The depth soil water responding to rainfall of the level terrace is deeper than the slope.Under the heavy rain condition,the infiltration depth of the rainwater in the P.orientalis forest is 90 cm(slope)-110 cm(level terrace),and in the P.tabuliformis forest is 60 cm(slope)-70 cm(level terrace).[Conclusions]It is recommended to use level terrace and select P.orientalis when planting soil and water conservation forests on the Loess Plateau.