[Characteristics of stable isotopes in soil water under several typical land use patterns on Loess Tableland].
[Characteristics of stable isotopes in soil water under several typical land use patterns on Loess Tableland].
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发表时间：
2012-03
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通讯作者：
Liping Cheng;Wenzhao Liu
中科院分区：
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作者：
Liping Cheng;Wenzhao Liu
以陕西省长武县黄土塬区为研究对象，对黄土塬区不同土地利用方式下的降水和0-20 m黄土剖面土壤水进行了同位素组成分析，旨在了解黄土塬区土壤水稳定同位素特征及土壤水运动机制。研究区大气降水稳定同位素含量具有明显的冬春季高、夏秋季低的季节变化特征，大气降水稳定同位素含量的线性方程为Δ D = 7.39 Δ 180 + 4.34（R2 = 0.94，n = 71）。土壤水中稳定同位素含量均落在低分子质量线的下方，且7 ~ 10月均高于降水中的含量，说明土壤水主要由稳定同位素含量较低的夏秋季降水补充。在不同土地利用方式的土壤剖面中，随土层深度的增加，土壤水稳定同位素含量趋于一致;而在同一土地利用方式下，浅层土壤水稳定同位素组成随时间变化较大，随深度增加变化较小。通过对降水和土壤水稳定同位素含量的比较，发现高原降水入渗过程中存在活塞流和优先流并存的现象，优先流的发生与土地利用方式有一定的关系。一般情况下，高耗水人工林造成的负水平衡引起的土壤干化可降低优先流发生的概率，而农田或天然草地则易发生降水以优先流形式入渗，从而补充深层土壤水或地下水。
In this study, the precipitation over the Loess Tableland in Changwu County of Shaanxi Province and the soil water in 0-20 m loess profiles under different land use patterns on the Tableland were sampled, and their isotope compositions were analyzed, aimed to understand the characteristics of stable isotopes in the soil water and the mechanisms of the soil water movement. In the study area, the equation of the local meteoric water line (LMWL) was deltaD = 7.39 delta180 + 4.34 (R2 = 0.94, n = 71), and the contents of the stable isotopes in the precipitation had an obvious seasonal variation of high in winter and spring and low in summer and autumn. The contents of the stable isotopes in the soil water were fell on the underside of the LMWL, and higher than those in the precipitation from July to October, indicating that the soil water was mainly replenished by the precipitation with lower stable isotope contents in summer and autumn. In the soil profiles of different land use patterns, the stable isotope contents in soil water tended to be the same with the increasing soil depth; while under the same land use patterns, the water's stable isotope composition in shallow soil layers changed greatly with time, but changed less with increasing depth. Through the comparison of the stable isotope contents in precipitation and in soil water, it was observed that the piston flow and preferential flow on the Tableland were coexisted in the process of precipitation infiltration, and the occurrence of the preferential flow had a certain relation with land use pattern. Generally, the soil desiccation caused by the negative water balance resulted from the artificial plantations of high water consumption could reduce the probability of preferential flow occurrence, whereas the precipitation infiltration in the form of preferential flow could easily occur on the farmland or natural grassland so that the soil water in deep layers or the ground water could be replenished.