Press Release
Quantifying transpiration from plants at the global scale---Details of the global hydrological cycle revealed by stable oxygen and hydrogen isotope ratio of water ---- Associate Professor Kei Yoshimura

Institute of Industrial Science


The research group lead by K. Yoshimura, including Z. Wei, K. Ono, W. Kim, has developed a new isotope measurement for partitioning evaportranspiration to estimate transpiration from plants on a global scale.The points of release are as follows:
≫Through 3-year-observation on rice paddy field, we developed a new isotope measurement for partitioning evapotranspiration and reached to estimate transpiration from plants accounted for about 57%±2s of global total terrestrial evapotranspiration.
≫During these few years, global-scale estimates of transpiration have been reported in a range of 20 to 90 % of total terrestrial evaportranspiration, and it has been an intensive discussion in the community. Our results will help to terminate these discussions.
≫Accurate estimation of transpiration, that is inevitable to accurately estimate carbon cycle through photosynthesis, is vitally important as basic information when we think how to mitigate and/or adapt the global climate changes.

Z. Wei, K. Yoshimura, A. Okazaki, W. Kim, Z. F. Liu, and M. Yokoi, "Partitioning of evapotranspiration using high-frequency water vapor isotopic measurement over a rice paddy field", Water Resources Research, doi: 10.1002/2014wr016737
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Z. Wei, K. Yoshimura, A. Okazaki, K. Ono, W. Kim, M. Yokoi, and C. T. Lai, "Understanding the variability of water isotopologues in near-surface atmospheric moisture over a humid subtropical rice paddy in Tsukuba, Japan", Journal of Hydrology , doi: 10.1016/j.jhydrol.2015.11.044
Article link

Z. Wei, K. Yoshimura, L. Wang, D. Miralles, S. Jasechko, and X. Lee, "Revisiting the contribution of transpiration to global terrestrial evapotranspiration", Geophysical Research Letters , doi:10.1002/2016GL072235
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Press Release:
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Kei Yoshimura, Associate Professor
Institute of Industrial Science, The University of Tokyo
TEL: +81 3 5452 6382
Fax: +81 3 5452 6383


Figure 1 Observation system for measuring stable isotopic composition of water vapor located on the test rice paddy field.

Figure 2
Daily averaged variation in isotope ratios of ET (blue circles), T (red squares), and E (pink diamonds). Two points of δE , which were less than -300 per mil, are not shown in this figure.
ET: terrestrial evapotranspiration
T: transpiration
E: open water evaporation
I: Interception
LAI: leaf area index

Figure 3.
Global distributions of the ensemble means of TI(E+T+I) (Reproduced from Z.Wei et al., 2017)

Figure 4
Comparison of TI(E+T+I) estimated by different methods. (Reproduced from Z.Wei et al. 2017)

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