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Research Project: Understanding Water-Driven Ecohydrologic and Erosion Processes in the Semiarid Southwest to Improve Watershed Management

Location: Southwest Watershed Research Center

Title: Ecosystem transpiration and evaporation: Insights from three water flux partitioning methods across FLUXNET sites

Author
item NELSON, J. - Max Planck Institute For Biogeochemistry
item PEREZ-PRIEGO, O. - Macquarie University
item ZHOU, S. - Columbia University
item POYATOS, R. - Centre For Ecological Research And Forestry Applications (CREAF)
item ZHANG, Y. - Columbia University
item BLANKEN, P.D. - Colorado State University
item GIMENO, T.E. - University Of Basque Country
item WOHLFAHRT, G. - University Of Innsbruck
item DESAI, A.R. - University Of Wisconsin
item GIOLI, B. - National Research Council - Italy
item LIMOUSIN, J. - University Of Montpellier
item BONAL, D. - Université De Lorraine
item PAUL-LIMOGES, E. - University Of Zurich
item Scott, Russell - Russ
item VARLAGIN, A. - Russian Academy Of Sciences
item FUCHS, K. - Karlsruhe Institute Of Technology
item MONTAGNANI, L. - Forest Service (FS)
item WOLF, S. - Eth Zurich
item DELPIERRE, N. - Université Paris-Saclay
item BERVEILLER, D. - Université Paris-Saclay
item GHARUN, M. - Eth Zurich
item MARCHESINI, L.B. - Fondazione Edmund Mach
item GIANELLE, D. - Fondazione Edmund Mach
item SIGUT, L. - Czech Academy Of Sciences
item MAMMARELLA, I. - University Of Helsinki
item SIEBICKE, L. - University Of Gottingen
item BLACK, T.A. - University Of British Columbia
item KNOHL, A. - University Of Gottingen
item HORTNAGL, L. - Eth Zurich
item MAGLIULO, V. - National Research Council - Italy
item CARVALHAIS, N. - Max Planck Institute For Biogeochemistry
item MIGLIAVACCA, M. - Max Planck Institute For Biogeochemistry
item REICHSTEIN, M. - Max Planck Institute For Biogeochemistry
item JUNG, M. - Max Planck Institute For Biogeochemistry

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2020
Publication Date: 12/1/2020
Citation: Nelson, J., Perez-Priego, O., Zhou, S., Poyatos, R., Zhang, Y., Blanken, P., Gimeno, T., Wohlfahrt, G., Desai, A., Gioli, B., Limousin, J., Bonal, D., Paul-Limoges, E., Scott, R.L., Varlagin, A., Fuchs, K., Montagnani, L., Wolf, S., Delpierre, N., Berveiller, D., Gharun, M., Marchesini, L., Gianelle, D., Sigut, L., Mammarella, I., Siebicke, L., Black, T., Knohl, A., Hortnagl, L., Magliulo, V., Carvalhais, N., Migliavacca, M., Reichstein, M., Jung, M. 2020. Ecosystem transpiration and evaporation: Insights from three water flux partitioning methods across FLUXNET sites. Global Change Biology. 26:6916-6930. https://doi.org/10.1111/gcb.15314.
DOI: https://doi.org/10.1111/gcb.15314

Interpretive Summary: Transpiration is the movement of water from plant leaves to the atmosphere by plants, and it is a key part of the hydrological cycle. Though it has been studied extensively in laboratories, plant growth chambers, and greenhouses, estimating transpiration over natural surfaces is extremely challenging. We apply and compare three new methods for estimating T using existing water and carbon flux measurements from 251 sites globally. The three different T estimates track each other well but a considerable spread in their average values is found. Overall, the global patterns of transpiration are plausible and qualitatively consistent among the different methods implying a significant advance made for estimating and understanding transpiration globally, while the magnitudes remain uncertain. These results represent the first extensive estimates of ecosystem T from EC data permitting a data driven perspective on the role of plants’ water use for global water and carbon cycling in a changing climate.

Technical Abstract: We apply and compare three widely applicable methods for estimating ecosystem transpiration (T) from eddy covariance (EC) data across 251 FLUXNET sites globally. All three methods are based on the coupled water and carbon relationship, but they differ in assumptions and parameterization. Intercomparison of the three daily T estimates shows high correlation among methods (R² between 0.80 and 0.87), but a spread in magnitudes of T/ET (evapotranspiration) from 45% to 77%. When compared at six sites with concurrent EC and sap flow measurements, all three EC based T estimates show higher correlation to sap flow based T than EC based ET. The partitioning methods recover expected tendencies of T/ET increasing with dryness (vapor pressure deficit and days since rain) and with leaf area index. Analysis of 140 complete site-years shows that T/ET variability was 1.6 times higher across sites than across years. Spatial variability of T/ET was primarily driven by vegetation and soil characteristics (e.g. crop or grass designation, minimum annual leaf area index, soil coarse fragment volume) rather than climatic variables. Overall, T and T/ET patterns are plausible and qualitatively consistent among the different water flux partitioning methods implying a significant advance made for estimating and understanding transpiration globally, while the magnitudes remain uncertain. Our results represent the first extensive estimates of ecosystem T from EC data permitting a data driven perspective on the role of plants’ water use for global water and carbon cycling in a changing climate.