长沙地区樟树林穿透水空间变异及稳定同位素特征

于2018年4月至2019年3月在长沙地区典型樟树林收集降水、穿透水和相应的冠层信息,分析穿透水量的空间变异及穿透水稳定同位素的特征,旨在揭示林冠层水文过程,为林地水文生态系统的科学管理提供参考。结果表明:樟树林下总穿透水量为340.1 mm,占林外总降水量的71.2%;受观测点距树干距离和冠层叶面积指数等因素的综合影响,穿透水量具有较大的空间变异,且在时间变化上相对稳定。分析表明,研究区穿透水量的空间变异系数随降水量增加而减小,体现了降水特征对穿透水空间变异的重要影响;相对穿透水量而言,穿透水稳定同位素组成受冠层结构和大气条件的影响较小,其空间变异较小,在时间变化上不稳定;大部分降水事件中穿透水稳定同位素较降水稳定同位素富集,但其平均值之间不具有显著性差异,说明穿透水在形成过程中经历了较弱的蒸发作用;穿透水与降水中稳定同位素和过量氘的偏离还暗示了冠层具有选择性穿透效应。

Spatial Variation and Stable Isotopic Characteristic of Throughfall Under Cinnamomum camphora Woods in Changsha

In order to reveal the hydrological process of the forest canopy and provide a reference for the scientific management of forest hydrological ecosystem, precipitation, throughfall, and canopy information were collected from typical Cinnamomum Camphora woods during April 2018 to March 2019 in Changsha to study the spatial variability of throughfall and the characteristic of stable isotopes in throughfall. The results showed that the total throughfall under the canopy was 340.1 mm, accounting for 71.2% of the total precipitation outside the forest; comprehensively affected by the canopy structure including the distance from tree trunk and the leaf area index. The throughfall presented great spatial variability and stable temporal variability.The correlation analysis showed that the coefficient of spatial variability decreased with the increase of precipitation, reflecting the important influence of precipitation characteristics on the spatial variation of throughfall.Compared with the amount of throughfall, the stable isotopic compositions in throughfall were hardly affected by canopy structure and atmospheric conditions,not obvious in spatial variation, and not stable in temporal variation. In most precipitation events,stable isotopes in throughfall were richer than those in precipitation, and there was no significant discrepancy between the mean values of them, indicating that throughfall underwent weak evaporation in its formation process. The deviation between the stable isotopes and d in throughfall and those in precipitation suggested that the canopy had the selective penetrating effect.