南方丘陵区降雨同位素组成及影响因素的研究——以长沙油茶林为例

Study on Isotopic Composition and Influencing Factors of Rainfall in Southern Hilly Region--A Case Study of Changsha Camellia oleifera Forest

为深入探究南方丘陵区油茶林地降雨同位素变化规律,揭示该森林系统水循环对水汽来源和气候的响应机理,利用向后轨迹模型(hybrid single particle lagrangian intergrated trajectory,HYSPLIT)对油茶林地不同水汽轨迹进行聚类分析,采用偏相关分析综合评估降雨同位素组成的主要影响因素。结果表明,林地降雨季风期(5—9月)水汽来源主要是印度洋(14%)和西太平洋(37%)输送的暖湿气团,非季风期水汽来源中75%以上来自局部蒸发水汽和南下冷空气;同位素组成表现出季风期贫乏,非季风期富集,呈现出“V”形的季节性变化规律。2019年林地降水线δD=8.3δ18O+13.5(R2=0.99),反映了林地的较低蒸发水平和湿润气候条件,林地降雨同位素存在显著的降雨量效应、风速效应和湿度效应,降雨量效应远远大于温度效应,湿度效应对于温度的变化十分敏感。以上结果为长沙油茶林地的水循环机理研究提供了理论参考,有利于指导地区水资源科学调控,促进林业生态发展。

In order to explore precipitation isotope variation of Camellia oleifera forest in southern hilly region,and reveal the response mechanism of water cycle in this forest system to water vapor source and climate,HYSPLIT(hybrid single particle lagrangian intergrated trajectory)was used for cluster analysis of different water vapor trajectory in Camellia oleifera forest,and partial correlation analysis was used to comprehensively evaluate the main influencing factors of rainfall isotope composition.The results showed that the water vapor source of Camellia oleifera forest during monsoon period(from May to September)was mainly the warm and humid air mass of the Indian Ocean(14%)and western of Pacific Ocean(37%),and more than 75%of the non-monsoon water vapor sourced from the local evaporation of water vapor and the cold air from the north.The isotopic composition was poor in monsoon period and enriched in non-monsoon period,which showed a“V”shaped seasonal variation pattern.In 2019,the precipitation line wasδD=8.3δ18O+13.5(R2=0.99),reflecting the low evaporation level and humid climate conditions of forest land.There were obvious precipitation effect,wind speed effect and humidity effect in forestland precipitation isotope,and the precipitation effect far overcomed the temperature effect,and humidity effect was very sensitive to temperature change.These above results provided a theoretical reference for the study of water cycle mechanism of Changsha Camellia oleifera forest,which was beneficial to guide the scientific control of regional water resources and promote the development of forestry ecology.