FLUXNET-CH4 synthesis activity: objectives, observations, and future directions

Authors: KNOX, SARA - Stanford University; JACKSON, ROBERT - Stanford University; POULTER, BENJAMIN - Nasa Goddard Institute For Space Studies; MCNICOL, GAVIN - Stanford University; FLUET-CHOUINARD, ETIENNE - Stanford University; ZHANG, ZHEN - University Of Maryland; HUGELIUS, GHUSTAF - Stockholm University; BOUSQUET, PHILIPPE - University Of Paris; CANADELL, JOSEP - Commonwealth Scientific And Industrial Research Organisation (CSIRO); SAUROIS, MARIELLE - University Of Paris; PAPALE, DARIO - University Of Paris; CHU, HOUSEN - Lawrence Berkeley National Laboratory; KEENAN, TREVOR - University Of California; BALDOCCHI, DENNIS - University Of California; MAMMARELLA, IVAN - University Of Helsinki; AURELA, MIKE - Finnish Meteorological Institute; BOHRER, GIL - The Ohio State University; CAMPBELL, DAVE - University Of Waikato; CESCATTI, ALESSANDRO - Michigan State University; CHAMBERLAIN, SAMUEL - University Of California; CHEN, JIQUAN - Michigan State University; DENGAL, SIGRID - University Of California; DESAI, ANKUR - University Of Wisconsin; EUSKIRCHEN, EUGENIE - University Of Alaska; FRIBORG, THOMAS - University Of Copenhagen; GOECKEDE, MATHIAS - McMaster University; HEIMANN, MARTIN - Finnish Meteorological Institute; HELBIG, MANUEL - McMaster University; KANG, MINSEOK - Seoul National University; KLAT, JANINA - Karlsruhe Institute Of Technology; KRAUSS, KEN - Karlsruhe Institute Of Technology; KUTZBACH, LARS - Universitat Hamburg; LOHILA, ANNALEA - Finnish Meteorological Institute; MITRA, BHASKAR - University Of Texas; MORIN, TIMOTHY - State University Of New York- College Of Environmental Science And Forestry; NILSSON, MATS - Swedish University Of Agricultural Sciences; NIU, SHULI - Chinese Academy Of Sciences; NOORMETS, ASKO - University Of Texas; OECHEL, WALTER - University Of Exeter; PEICHL, MATTHIAS - Swedish University Of Agricultural Sciences; PELTOLA, OLLI - Finnish Meteorological Institute; Reba, Michele; RUNKLE, BENJAMIN - University Of Arkansas; RYU, YOUNGRYEL - Seoul National University; SACHS, TORSTEN - University Of Potsdam; SCHÄFER, KARINA - Rutgers University; SHURPALI, NARASINHA - University Of Eastern Finland; SONNENTAG, OLIVER - Genome Quebec; TANG, ANGELA - Universiti Malaysia Sarawak; VESALA, TIMO - University Of Helsinki; WARD, ERIC - Us Geological Survey (USGS); WINDHAM-MYERS, LISAMARIE - Us Geological Survey (USGS); ZONA, DONATELLA - University Of Sheffield

Submitted to: Bulletin of the American Meteorological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2019
Publication Date: 1/7/2020
Citation: Knox, S.H., Jackson, R.B., Poulter, B., Mcnicol, G., Fluet-Chouinard, E., Zhang, Z., Hugelius, G., Bousquet, P., Canadell, J.G., Saurois, M., Papale, D., Chu, H., Keenan, T.F., Baldocchi, D., Mammarella, I., Aurela, M., Bohrer, G., Campbell, D., Cescatti, A., Chamberlain, S., Chen, J., Dengal, S., Desai, A.R., Euskirchen, E., Friborg, T., Goeckede, M., Heimann, M., Helbig, M., Kang, M., Klat, J., Krauss, K.W., Kutzbach, L., Lohila, A., Mitra, B., Morin, T.H., Nilsson, M.B., Niu, S., Noormets, A., Oechel, W.C., Peichl, M., Peltola, O., Reba, M.L., Runkle, B.R., Ryu, Y., Sachs, T., Schäfer, K.V., Shurpali, N., Sonnentag, O., Tang, A.C., Vesala, T., Ward, E.J., Windham-Myers, L., Zona, D. 2020. FLUXNET-CH4 synthesis activity: objectives, observations, and future directions. American Meteorological Society. 100(12):2607-2632. https://doi.org/10.1175/bams-d-18-0268.1.
DOI: https://doi.org/10.1175/bams-d-18-0268.1

Interpretive Summary: Greenhouse gas fluxes are important worldwide. Currently a well-coordinated effort synthesizing CO2 flux measurements through a network exists. No such network exists for methane. The manuscript describes the formation of a new FLUXNET coordination network for methane measurements organized by the Global Carbon Project in partnership with other initiatives and regional flux networks. An initial analysis of the eddy covariance methane dataset suggests many similarities, but important differences in methane emissions reported regionally and by ecosystem type compared to previous syntheses of chamber-based measurements. Through the analysis and synthesis of eddy covariance methane measurements, the long-term goal is to better characterize methane fluxes and predictive variables from terrestrial ecosystems, reconcile differences between bottom-up and top-down methane budgets, and inform and validate earth-system models.

Technical Abstract: Unlike well-coordinated efforts for synthesizing CO2 flux-tower observations (e.g. FLUXNET), no such network and data synthesis effort exist for CH4. This paper describes the formation of a new FLUXNET coordination network for CH4 measurements organized by the Global Carbon Project in partnership with other initiatives and regional flux networks. This manuscript provides the objectives of the initiative, an overview of the coverage of eddy covariance CH4 flux measurements globally, initial results comparing CH4 fluxes across 49 sites, and future research directions and needs. An initial analysis of the eddy covariance CH4 dataset suggests many similarities, but important differences, in CH4 emissions reported regionally and by ecosystem type compared to previous syntheses of chamber-based measurements; average growing CH4 emissions for tundra wetlands in the present eddy covariance database, for instance, was approximately one quarter of the value reported in chamber-based syntheses, whereas fluxes in temperate wetlands were up to 70% higher. Average annual soil and air temperature were found to be the strongest predictor of annual CH4 flux across wetland sites. A significant increase in the ratio of annual CH4 to ecosystem respiration along geographic temperature gradients was also observed. Follow-up analyses will be important using additional sites and meta-data, though, particularly because water-table depth was reported for only half of the sites. Through the analysis and synthesis of eddy covariance CH4 measurements, the long-term goal is to better characterize CH4 fluxes and predictive variables from terrestrial ecosystems, reconcile differences between bottom-up and top-down CH4 budgets, and inform and validate earth-system models.