基于稳定同位素的SPAC系统水分转化研究进展

Research progresses on stable isotopes of water transformation in SPAC system

大气⁃土壤⁃植被连续体(soil⁃plant⁃atmosphere continuum,SPAC)系统水分转化过程是生态水文学重要的研究内容。稳定同位素作为天然的示踪剂能有效示踪、整合和指示SPAC系统中的水分输入、输出以及转化过程。笔者在简述稳定同位素应用原理的基础上,以垂直方向上SPAC系统水分运移的视角,阐释基于稳定同位素技术的土壤⁃根系界面水分运移、植物传输水分中存在的分馏和植物冠层⁃大气界面水分交换的研究进展,探讨了SPAC系统水分转化研究中稳定同位素技术在分馏机制、时间分辨率与空间异质性方面的局限性。认为未来基于稳定同位素的SPAC水分转化研究还需着重在以下3个方面进行:①借助广泛应用于其他领域的便携式同位素分析仪对各种同位素水池同位素组成进行原位观测;②结合多种同位素分析水体同位素组成来分析土壤⁃根系界面水分运移过程,进一步确定树木水分来源,提高识别和划分的准确性,并以此完善稳定同位素应用模型;③利用同位素标记盆栽实验精准控制叶片吸水的水源,高分辨率地解析叶片吸水的发生位置以及时间;④结合控制性同位素标记实验并利用离心技术提取木质部导管中的汁液水,对比分析各水池同位素偏差,以深入开展同位素分馏机制的研究。

The water conversion process of the soil⁃plant⁃atmosphere continuum(SPAC)system is an important research topic in ecological hydrology.Stable isotopes,as natural tracers,can effectively trace,integrate and indicate water input,output and transformation processes in the SPAC system.Based on a brief introduction of the application principle of stable isotopes,this study reviewed the progress of research within the context of vertical water transport at the soil⁃root interface;fractionation in plant water transport;and water exchange at the plant canopy⁃atmosphere interface based on stable isotope techniques.This study explored the limitations of stable isotopic techniques in terms of elucidating fractionation processes,temporal resolution and spatial heterogeneity in water transformation studies of SPAC systems.Finally,we conclude by providing corresponding suggestions for the future application and development of stable isotope technology.Specifically,we recommend that future research within the context of spac water conversion based on stable isotopes should focus on the following three aspects:(1)In situ observation of the isotopic composition of various isotopic pools with the help of portable isotopic analyzers.(2)Multi isotope analysis of pool isotope composition to analyze the water transport process at the soil root interface,to further determine the water source of trees,and subsequently improve the accuracy of source identification and division,and improve the stable isotope application model.(3)Using isotope labeled pot experiments to accurately control the water source of leaf water absorption,and to analyze the location and time of leaf water absorption at a more fine level.(4)Using controlled isotope labeling and centrifugal technology to extract juice from xylem vessels,the isotope deviation of each pool was compared and analyzed to further study the isotope fractionation mechanisms.