摘要
自然降水是半干旱黄土区土壤水分的唯一来源.为了探究黄土丘陵区深厚土壤干化背景下再种植深根系、多年生植物后的土壤水分入渗对降雨的响应特征,本研究在宁夏南部王洼水土保持试验站采用野外实地大规格土柱模拟干燥化土壤的方法种植苜蓿,试验分析2022-2023年每年的3-10月定位观测数据.结果表明:1)能有效产生土壤水分入渗的降雨次数仅占总降雨次数的41.67%,降雨量与入渗量占比为:小雨入渗量占其降雨量的15.89%,中雨入渗量占其降雨量的35.63%,大雨入渗量占其降雨量的52.20%,暴雨入渗量占其降雨量的61.50%,入渗量随着降雨量的增大呈增大的趋势;2)降雨入渗深度小于 30 cm的降雨次数占总降雨次数的 76.04%,入渗深度在30～80 cm的降雨次数占总降雨次数的18.75%,入渗深度在80 cm以上的降雨次数占总降雨次数的5.21%;3)深层土壤干化背景下种植苜蓿,一龄苜蓿地月尺度土壤剖面水分呈现增加趋势,二龄苜蓿地月尺度土壤剖面水分呈减小趋势,逐月降雨入渗深度(Zm)随月降雨量(Pm)增加呈二次函数增大变化:Zm=-0.0101Pm2+3.9426Pm(R2=0.9895).本研究可为黄土高原区深厚土壤严重干化后再植深根系、多年生植物及其可持续发展提供理论与数据支撑.
Abstract
Natural precipitation is the only water source in the semi-arid loess region.This research investigated the characteristics of soil water infiltration following precipitation after replanting deep-rooted,perennial plants in soil with severely depleted moisture levels in the hilly areas of the Loess Plateau.Specifically,the research simulated the cultivation of Medicago sativa,using large-scale soil columns(lysimeters)at the Wangwa Soil and Water Conservation Experiment Station in southern Ningxia.The simulation experiment was based on actual rainfall data from March to October in 2022-2023.The results indicated that:1)Only 41.67% of all precipitation events resulted in soil water infiltration.The ratio of infiltration to precipitation varied with rainfall intensity:in light rain,moderate rain,heavy rain and torrential rain the infiltration was,respectively,15.89%,35.63%,52.20% and 61.50% of the total precipitation.Infiltration amounts thus showed an increasing trend with increasing precipitation.2)Precipitation infiltrating to depths of less than 30 cm,to depths of 30-80 cm,and to depths greater than 80 cm,accounted for,respectively,76.04%,18.75% and 5.21% of the total precipitation.3)With respect to the issue of deep soil water depletion,alfalfa cultivation led to a trend of soil water increase in soil water measured monthly for one year old plants,while for two year old plants,soil water measured monthly showed a decreasing trend.The monthly infiltration depth(Zm)increased with increasing monthly precipitation(Pm)as a quadratic function:Zm=-0.0101Pm2+3.9426Pm(R2=0.9895).The study provides data on deep soil water status,useful for planning the replanting and sustainable development of deep-rooted,perennial plants in areas on the Loess Plateau with severely dried deeper soil horizons.
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