晋西黄土区典型林地土壤水分变化特征

选择晋西黄土区蔡家川流域5种典型林地(山杨×辽东栎天然次生林、人工油松×刺槐混交林、人工油松林、人工刺槐林、人工侧柏林)作为研究对象,在每块样地中心布设1个土壤水分观测点,采用TRIME-TDR土壤水分测定仪定位观测2016—2018年1—12月的土壤体积含水量,测定深度为200 cm,每20 cm为1个测层,每月分上、中、下旬进行土壤水分含量观测,分析不同林地类型土壤水分年内变化规律和土壤水分垂直变化规律。结果表明:(1)研究区不同林地土壤水分年内变化可以划分为稳定期(1—3月)、波动期(4—6月)、增长期(7—9月)和消耗期(10—12月)4个时期,5种林分类型的年平均土壤储水量按照从大到小的排序为天然次生林地(338.68 mm)>人工油松林地(319.74 mm)>人工侧柏林地(314.15 mm)>人工油松×刺槐混交林地(303.37 mm)>人工刺槐林地(292.03 mm),刺槐林地耗水量最大。(2)在雨季末,研究区5种林分类型林地土壤水分均得到了正向补充,且土壤水分的恢复能力大小排序为次生林地>针叶林地>混交林地>刺槐纯林。(3)研究区土壤水分垂直变化可划分为土壤水分含量速变层和土壤水分含量相对稳定层2个层次;随着土层深度增加,不同林地类型剖面平均含水量总体上先增大后减小。不同林地类型表层土壤水分含量为侧柏林地>次生林地>油松林地>油松×刺槐混交林地>刺槐林地;土壤水分的补充深度为天然林地>针叶林地>油松×刺槐混交林地>刺槐纯林。

Soil Moisture Dynamics of Typical Plantation in Loess Region of West Shanxi

In this study, five typical forest lands (Poplar Populus×Quercus liaotungensis natural secondary forest, Pinus tabulaeformis×Robinia pseudoacacia mixed forest, artificial Pinus tabulaeformis forest, artificial Robinia pseudoacacia forest, and artificial Platycladus orientalis forest) in the Caijiachuan watershed of the loess area in west Shanxi were selected as the research object. A soil moisture observation point was placed in the center of each plot, and the soil volumetric water content from January 2016 to December 2018 were determined by the TRIME-TDR soil moisture analyzer, and the soil moisture in 0-200 cm soil layer was determined stratified with every 20 cm respectively in the early, middle and late of each month. Then the annual variation and the vertical variation of soil moisture in different forest types were analyzed. The results showed that (1) annual variation of soil moisture in different forest lands in this study area could be divided into four periods, including stationary period (January-March), fluctuation period (April-June), growth period (July-September) and consumption period (October-December), and the average soil water storage of the five forest types during the year followed the order of the natural secondary forest land (338.68 mm) > artificial P. tabulaeformis forest (319.74 mm) > artificial P. orientalis forest (314.15 mm) > the mixed forest land(303.37 mm) > the R. pseudoacacia forest (292.03 mm), and the water consumption of R. pseudoacacia forest land was the highest. (2) At the end of the rainy season, the soil moisture of the five forest types in the study area was positively supplemented, and the soil water recovery capacity followed the order of natural secondary forest land > coniferous forest land > mixed forest land > R. pseudoacacia forest land. (3) The vertical change of soil moisture in the study area could be divided into two layers, including the rapid change layer of soil moisture content and the relatively stable layer of soil moisture content. As the soil layer depth increasing, the average water content of different forest profiles generally increased first and then decreased. Surface soil moisture content of different forest types followed the order of P. orientalis forest > natural secondary forest land > P. tabulaeformis forest > mixed forest land > R. pseudoacacia plantations. Replenishment depth of soil moisture followed the order of natural secondary forest land > coniferous forest land > mixed forest land > R. pseudoacacia forest land.