植被截留对降水同位素分布的试验研究

Application of Stable Usotope to Study the Influence of Vegetation Interception on Precipitation Distribution

植被截留对于探究小流域降雨空间变化原因以及深入理解产流机制具有重要的意义.本文通过对长江中下游小流域梅雨降水事件的林外降水和贯穿降水水样的稳定同位素(δ^18O和δ^2H)进行分析,探究贯穿降水同位素时空变化原因.通过拟合林外降水的δ^18O和δ^2H得到和睦桥流域梅雨事件大气降水线,其斜率和截距接近全球大气水线,但与中国东部季风区的大气水线存在明显的差别,主要是受采样方法、下垫面条件、气候环境和降水类型的综合作用.降水事件中的贯穿降水比林外降水的氘盈余平均值高,这可能与植被的截留以及强烈的蒸发有关.林外降水和贯穿降水的稳定同位素在时间尺度上的变化存在着明显的不同,总的来说贯穿降水相对更加贫化,这可能由蒸发分馏和雨强共同影响.贯穿降水的同位素展示明显的空间变化,主要由植物截留以及流域地形共同影响.

Vegetation interception is of great significance for exploring the factors which controls the spatial variability of rainfall and for understanding the runoff generation mechanism in small watershed covered with bamboo.This study investigates the stable isotopic(δ^18O and δ^2H)of precipitation and throughfall in Hemuqiao watershed in the lower reaches of the Yangtze River during the plum rainfall events to explore the spatial and temporal variability.The Meteoric Water Line is established by using the relationship between δ^18O and δ^2H.The results show that the slope and intercept are close to the Global Meteoric Water Line,but there is a significant difference from the Meteoric Water Line in the eastern monsoon region of China due to the sampling methods,underlying surface condition and the type of precipitation.The average values of d-excess of throughfall are higher than that of precipitation,which may be related to vegetation interception and evaporation fractionation effect.There are significant differences in the variation of stable isotopic composition of precipitation and throughfall in temporal.In general,the isotopic composition of precipitation is relatively more depleted,which may be affected by both evaporation fractionation and rainfall intensity.The isotopic of throughfall exhibits significant spatial variations,mainly due to vegetation interception and watershed topography.