Water isotope analysis for tracing ecosystem processes: measurement techniques,ecological applications,and future challenges

Stable oxygen and hydrogen isotope analysis provides an important tool to trace, integrate or indicate water fluxes from leaf, whole-plant to ecosystem levels. Through measuring and analyzing the natural varitions in the hydrogen and oxygen isotope compositions of water from different components of ecosystem, we can partition evapotranspiration of ecosystem, determine source of plant water uptake, and study mechanism of leaf water isotope enrichment. As such, water isotope analysis has emerged as an indispensable technique to study the mechanism and ecological effects of different water cycle processes in ecosystem. In this paper, we briefly reviewed the history in development and application of water isotope analysis for terrestrial ecosystem studies, which then followed by more detailed introduction of the application principles and technical essentials. Furthermore, we reviewed progresses in diverse water-isotope based research field ranging from evapotranspiration partitioning, plant water uptake apportionment, sourcing of dew flux and precipitation vapor, to exploration leaf water isotope enrichment mechanisms and water-carbon coupling. Finally, we summarized technological and methodological challenges to be solved in the future ecological research, so as to fully realize the potential of water isotope analysis in various field of ecological research.