氢氧稳定同位素技术在生态系统水分耗散中的应用研究进展

Application of Hydrogen and Oxygen Stable Isotopes Technique in the Water Depletion of Ecosystems

氢氧稳定同位素作为水的"DNA",对于研究水分的传输和转化具有重要的意义,而水分耗散是水循环的重要组成部分。简单介绍氢氧稳定同位素在水分耗散研究中应用的主要原理和比较新的一些技术方法,主要对其在森林、草原生态系统和农田生态系统中蒸散发分离,植物水分来源区分、叶片水同位素富集和水分利用效率等方面做较为详细的归纳总结和探讨,最后指出国内此类研究仍然存在的问题和可能的发展方向,以期对未来氢氧稳定同位素技术在水分循环和水分耗散方面的应用研究有借鉴作用。

Stable isotopes of oxygen and hydrogen play an important role in the research on water transport and exchange.The composition of deuterium（D or 2H） and oxygen 18（18O） in water is very stable,which would not change with time unless fractionation happens.Therefore,they are good fingerprint of water movement.The fractional process of stable isotope is the key for tracing water cycling and transfer.Fractionation leads to the heavy isotopes enrichment of water evaporation vapor.And isotope composition of plant transpiration vapor is similar to the soil water absorbed by the roots except some halophilous plants.Measurement technologies for the isotope composition are mass-spectrometric method and laser method.Water depletion structure was partitioned by the combination of isotopic method and other method like the eddy covariance system.The plant transpiration accounted for about 6%-90% in different ecosystems or for different growth periods.Isotope compositions of different water sources were compared for the judgment of main root uptake layers.The application of hydrogen,oxygen and carbon isotopes in the leaf water-carbon coupling research revealed that 18O was enriched because of the photosynthesis and transpiration.As the composition of carbon dioxide and water,isotope compositions of 18O,2H and 13C in leaves could also be used to show the change of water use efficiency which was calculated by the carbon accumulation and water depletion.There still existed some problems in the application of this technique like the upscaling and impact factors analysis while some possible improvements were discussed.