北京山区典型植被土壤水分对次降雨的响应

Response of soil moisture of typical vegetation to individual rainfall in Beijing mountain area

为了揭示北京山区不同植被类型土壤水分对不同强度降雨的响应过程,选取北京山区内侧柏、荆条灌丛、荒草地为研究对象,基于2022年6—10月降雨和土壤水分的连续观测数据,分析土壤水分对不同降雨事件的响应特征。结果表明:(1)观测期内研究区降雨事件主要由小雨构成,小雨事件的总降雨量占总降雨量的14.78%,小雨事件对土壤水分的响应深度可达到40—60 cm土层;中雨、大雨、暴雨事件的总降雨量占总降雨量的85.52%,中雨、大雨、暴雨事件对土壤水分的响应深度均可达到60—80 cm土层;大降雨事件对土壤水分的补给作用更明显,降雨量越大,降雨能补给的土层深度越深,土壤水分补给效果越好。(2)三种植被平均土壤水分补给速率大小依次为荒草地>侧柏>荆条灌丛,说明降雨对荒草地的补给效果最好;土层活跃程度对植被土壤水分有影响,土层越活跃,土壤水分波动越大,三种植被平均土壤水分变异系数大小依次为荒草地>荆条灌丛>侧柏,而三种植被平均土壤储水量大小则依次为侧柏>荒草地>荆条灌丛,说明侧柏的土壤水分最为稳定。(3)荒草地、荆条灌丛剖面上各层土壤水分逐渐减少,侧柏则增加,说明土壤水分剖面分布受植被类型影响;侧柏、荆条灌丛、荒草地平均最大补给速率均发生在20—40 cm土层,说明降雨对浅层土壤水分的补给最为明显,对0—40 cm土层土壤水分的补给效果要更好。研究成果进一步解释了北京山区生态系统水分运动规律,为易干旱生态脆弱地带生态环境建设提供依据。

In order to reveal the response process of soil moisture of different vegetation types to rainfall of different intensities in Beijing mountain areas,Platycladus orientalis,Vitex negundo var,heterophylla shrubland,and native grassland were selected as the research objects.Based on the continuous observation data of rainfall and soil moisture from June to October 2022,the response characteristics of soil moisture to different rainfall events were analyzed.The results showed that:(1)during the observation period,the rainfall events in the research area were mainly consisted of light rain,with the total rainfall of the light rain event accounted for 14.78%of the total rainfall.The response depth of light rain events to soil moisture could reach 40—60 cm soil layer.The total rainfall of moderate rain,heavy rain and rainstorm events accounted for 85.52%of the total rainfall,the response depth of moderate rain,heavy rain,and rainstorm events could reach 60—80 cm soil layer.The replenishment effect of heavy rainfall was more obvious.The greater the rainfall,the deeper the soil layer that could be replenishment by rainfall,and the better the soil water replenishment effect.(2)The average soil water replenishment rate of the three vegetation was in the order of native grassland>Platycladus orientalis>Vitex negundo var,heterophylla shrubland,it indicated that rainfall had the best replenishment effect on native grassland.The active degree of soil layer had influence on soil moisture of vegetation.The more active the soil layer,the greater the fluctuation of soil moisture.The average soil moisture variation coefficient of the three vegetation types was in the order of native grassland>Vitex negundo var,heterophylla shrubland>Platycladus orientalis,while the average soil water storage capacity of the three vegetation types was in the order of Platycladus orientalis>native grassland>Vitex negundo var,heterophylla shrubland,indicating that Platycladus orientalis had the most stable soil moisture.(3)The soil moisture in each layer of the native grassland and the Vitex negundo var,heterophylla shrubland profile decreased gradually,while that of Platycladus orientalis increased,indicating that the distribution of soil moisture profile was influenced by vegetation types.The average maximum replenishment rate of Platycladus orientalis,Vitex negundo var,heterophylla shrubland,and native grassland occurred in the soil layer of 20—40 cm,indicating that rainfall had the most obvious replenishment effect on shallow soil moisture,and the replenishment effect on 0—40 cm soil moisture was better.The results further explained the law of water movement in the mountain ecosystem of Beijing,and provided a basis for the ecological environment construction in the fragile ecological zone prone to drought.