FLUXNET-CH4 Synthesis Activity: Objectives, Observations, and Future Directions

This paper describes the formation of, and initial results for, a new FLUXNET coordination network for ecosystem-scale methane (CH4) measurements at 60 sites globally, organized by the Global Carbon Project in partnership with other initiatives and regional flux tower networks. The objectives of the effort are presented along with an overview of the coverage of eddy covariance (EC) CH4 flux measurements globally, initial results comparing CH4 fluxes across the sites, and future research directions and needs. Annual estimates of net CH4 fluxes across sites ranged from −0.2 ± 0.02 g C m–2 yr–1 for an upland forest site to 114.9 ± 13.4 g C m–2 yr–1 for an estuarine freshwater marsh, with fluxes exceeding 40 g C m–2 yr–1 at multiple sites. Average annual soil and air temperatures were found to be the strongest predictor of annual CH4 flux across wetland sites globally. Water table position was positively correlated with annual CH4 emissions, although only for wetland sites that were not consistently inundated throughout the year. The ratio of annual CH4 fluxes to ecosystem respiration increased significantly with mean site temperature. Uncertainties in annual CH4 estimates due to gap-filling and random errors were on average ±1.6 g C m–2 yr–1 at 95\% confidence, with the relative error decreasing exponentially with increasing flux magnitude across sites. Through the analysis and synthesis of a growing EC CH4 flux database, the controls on ecosystem CH4 fluxes can be better understood, used to inform and validate Earth system models, and reconcile differences between land surface model- and atmospheric-based estimates of CH4 emissions.

KNOX Sara H.;  JACKSON Robert B.;  POULTER Benjamin;  MCNICOL Gavin;  FLUET-CHOUINARD Etienne;  ZHANG Zhen;  HUGELIUS Gustav;  BOUSQUET Philippe;  CANADELL Josep G.;  SAUNOIS Marielle;  PAPALE Dario;  CHU Housen;  KEENAN Trevor;  BALDOCCHI Dennis;  TORN Margaret;  MAMMARELLA Ivan;  TROTTA Carlo;  AURELA Mika;  BOHER Gil;  CAMPBELL David;  CESCATTI Alessandro;  CHAMBERLAIN Samuel;  CHEN Jiquan;  CHEN Weinan;  DENGEL Sigrid;  DESAI Ankur R.;  EUSKIRCHEN Eugenie;  FRIBORG Thomas;  GASBARRA Daniele;  GODED BALLARIN Ignacio;  GOECKEDE Mathias;  HEIMANN Martin;  HELBIG Manuel;  HIRANO Takashi;  HOLLINGER David;  IWATA Hiroki;  KANG Minseok;  KLATT Janina;  KRAUSS Ken W.;  KUTZBACH Lars;  LOHILA Annalea;  MITRA Bhaskar;  MORIN Timothy H.;  NILSSON Mats B.;  NIU Shuli;  NOORMETS Asko;  OECHEL Walter;  PEICHL M.;  PELTOLA Olli;  REBA Michele L.;  RICHARDSON Andrew D.;  RUNKLE Benjamin R.K.;  RYU Youngryel;  SACHS T.;  SCHÄFER Karina V.R.;  SCHMID Hans Peter;  SHURPALI N.;  SONNENTAG Oliver;  TANG Angela C.I.;  UEYAMA Masahito;  VARGAS Rodrigo;  VESALA T;  WARD Eric J.;  WINDHAM-MYERS Lisamarie;  WOHLFAHRT G.;  ZONA Donatella; 

2020-02-17

AMER METEOROLOGICAL SOC

JRC116217

0003-0007 (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC116217,   

10.1175/BAMS-D-18-0268.1 (online),