黄土沟壑区不同树龄侧柏林地土壤水分动态特征

Dynamic Characteristics of Soil Moisture for Different Age of Platycladus Orientalis in Gully Region of Loess Plateau

[目的]研究黄土沟壑区侧柏林地土壤水分动态特征,为黄土沟壑区退耕还林、生态建设以及人工侧柏林地的经营管理工作提供支持。[方法]以黄土沟壑区典型小流域南小河沟流域内5,25以及35a树龄侧柏为研究对象,使用烘干法对其生长季0—100cm土层土壤水分进行观测,并对其时空分布特征、土壤层次以及各层次干燥化特征进行分析。[结果](1)降雨对侧柏林地土壤水分的补给深度集中在0—40cm范围内,侧柏根系吸水主要作用范围则分布在40—100cm土层中。(2)3种树龄侧柏生长季0—100cm土层中的土壤水分的时间变化可以分为恢复期(5月)与消耗期(6—9月)。在恢复期,树龄对于土壤水分分布的影响不大,5,25与35a侧柏0—100cm土层蓄水量分别分布在230.3~304.2mm,177.7~249.7mm以及202.2~283.6mm。在消耗期,10—40cm土层中,土壤水分分布表现为:5a侧柏>35a侧柏>25a侧柏,而在60—100cm土层中,则表现为:5a侧柏>25a侧柏>35a;3种树龄侧柏林地0—100cm土层蓄水量则分布在131.2~207.2mm,123.4~220.8mm以及109.6~204.7mm。(3)在恢复期,5a侧柏林地各垂直分层土壤水分干燥化指数(SDI)差异不大,25与35a侧柏林地SDI在活跃层与过渡层随着深度的增大而增大。在根系作用层,25与35a侧柏林地SDI保持相对稳定。在消耗期,3种树龄侧柏林地SDI在活跃层较小,在过渡层随深度增大而增大,而在根系作用层保持相对稳定。[结论]与恢复期相比,在消耗期,3种树龄侧柏林地土壤水分变化剧烈程度均显著增大,其根系吸水能力随树龄增大而增大。

[Objective]Studying of dynamic characteristics of soil water in the gully region of Loess Plateau is very important to provide supports for the constructions of forest,ecological restoration and management of Platycladus orientalis.[Methods]Sites of 5,25 and 35 aPlatycladus orientalis in typical small basin（Nanxiaohegou basin）in the gully region of Loess Plateau were selected,where the soil moistures in growingseason were observed with drying method.On the basis of this,the spatial and temporal distributions of soil moisture in different layers and the desiccation characteristics of each layer were analyzed.[Results]（1） The rainfall recharged depth on soil moisture of the Platycladus orientalis concentrated in 0—40 cm while the effect of Platycladus orientalis＇ roots on soil moisture concentrated in 40—100 cm.（2） The temporal variation of0—100 cm soil moisture during growth season can be divided into recovery period（May）and depletion period（Jun.to Sept.）.In the recovery period,the age of the Platycladus orientalis had little effect on soil water distribution.The water storages of 5 a,25 aand 35 aPlatycladus orientalis in 0—100 cm varied between230.3~304.2 mm,177.7~249.7 mm and 202.2~283.6 mm,respectively.In the depletion period,the soil moistures of 10—40 cm in different sites ranked：5 a35 a25 a;while in 60—100 cm,the rank was 5 a25 a35 a.The 3 sites＇ water storages of 0—100 cm varied between 131.2~207.2 mm,123.4~220.8 mm and 109.6~204.7 mm,respectively.（3） In the recovery period,there was little difference for the SDIs among different soil layers;while the SDIs in the active layer and transition layer of 25 aand 35 asites increased with the increase of depth.For root affected layer,its value was relatively stable.In the depletion period,SDI value of the Platycladus orientalis was smaller in the active layer and increased with the increase of depth in the transition layer.For the root layer,the value was relatively stable.[Conclusion]As compared with it in the recovery period,the change degree of soil moisture increased significantly in the depletion period,and the absorption capacity of root increased in older Platycladus orientalis site.