喀斯特地区黄壤坡面土壤水分对降雨的响应

土壤水分是喀斯特地区水文生态环境的重要因素。通过在不同土地利用设置试验点,对降雨和20,40,80,100 cm深度土壤水分进行监测分析,揭示不同土地利用条件下土壤水分在降雨过程中的变化规律。结果表明:(1)植被盖度、土壤前期贮水量等因素对土壤水分的降雨补给量和土壤水分在土壤剖面上的再分配具有明显的影响。(2)土壤水分的降雨补给量在土壤剖面上的分布具有一定的层次性,随土层深度的增加整体表现为先增加后减少再增加的趋势;表层降雨补给量最小,最大降雨补给量多出现在100 cm深度。(3)土壤水分对降雨的响应具有滞后效应,并随土层深度增加而增强,随盖度增加而减弱。(4)在降雨影响阶段,可将土壤水分变化分为滞后期、上升期和消退期3个阶段;降雨过程中,植被盖度越高,降雨强度越大,土壤水分变化越快,并随着土层深度的增加减缓。研究结果为水资源的合理利用和配置以及水土保持提供参考和理论依据。

Response of Soil Moisture to Rainfall on Karst Yellow Soil Slope

Soil moisture is an essential variable in hydrology and ecology in karst region. In order to reveal the change rules of soil moisture during rainfall event, we monitored and analyzed the relationship between rainfall and soil moisture contents at 20 cm, 40 cm, 80 cm and 100 cm depth below surface in the grassland, cropland and bare land in Guizhou Province. Soil moisture was monitored by the ECH2O monitoring system and the EM50 data collector. The rainfall amount was collected by HOBO automatic weather station, and its measurement accuracy was 0.2 mm. The results showed that:(1) Vegetation cover, initial soil moisture content and rainfall density showed great influence on rainfall replenishment and redistribution of soil moisture in the soil profile. (2) To a certain extent, soil moisture affected by rainfall replenishment was not uniform in soil profile, which showed an up-down-up trend with the increase of soil depth, and 100 cm layer had the biggest rainfall replenishment compared with other layers. (3) The period in which soil moisture affected by rainfall could be divided into 3 stages:lag stage, rise stage and decline stage; as vegetation cover increased and rainfall density enhanced, the lag stage ended early, and the rise stage and decline stage started early. (4) The hysteresis effect in the lag stage enhanced with the increasing soil depth but receded with the increasing vegetation coverage. These results could provide a reference and theoretical basis for rational utilization and allocation of water resources and soil and water conservation.