黄土丘陵沟壑区不同土地利用方式的土壤水分效应

采用定位监测法,对黄土丘陵沟壑区的延安燕沟不同土地利用方式下土壤水分动态变化规律进行了系统分析。结果表明,在2002年降雨前期较多后期较少的情况下,土壤水分4—10月间呈现总体下降趋势,降雨对土壤水分的补偿效应明显不足;不同植被下土壤水分季节变化存在明显差异,苹果园和退耕坡地土壤水分衰减幅度小,林灌草地则水分逐渐减小,变化幅度较大;植被对土壤水分的差异性利用使得土壤平均水分含量以及水分剖面分层均存在差异。各层土壤水分变异系数的垂直变化也因植被类型的不同而存在差异。除浅层0—10 cm外,不同层次土壤水分变化趋势较缓和,较一致。土壤含水量逐月下降,个别月份水分略有升高,说明降雨对土壤水分的补偿作用在该降雨年型下表现微弱。

Soil Moisture Dynamics Under Differewt Land Uses in Hilly and Gully Area on Loess Plateau

Based on data collected by random survey of soil moisture in loess hilly and gully region, the authors analyzed the soil moisture dynamics of different land uses. The study showed that land uses resulted in the differences of dynamic characteristics of soil moisture. The crop land and the apple-orchard land had the same dynamics variation, With the process of time, soil moisture increased gradually and then fell, The lands without human husbandry, such as forest, shrub and grass land had the different trend. The soil moisture reduced gradually with time. In rainy season, soil moisture appreciably increased, but its extent was not markedly. At the same time, land uses also made the dynamic characteristics of soil moisture profile different. The authors used standard deviation to separate the layer of the soil vertical moisture variation. The result indicated that the active moisture layer of farm land was markedly shallow. Land uses of different types made the variation coefficients and their variety different. Except for the 0-10 cm layer, the variation trend of different layers is accordant. As a whole, soil moisture reduced gradually month by month. The expiation of rainfall was impaired by vegetation transpiration and soil evaporation.