FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities

Authors

Dennis Baldocchi, University of California, Berkeley
Eva Falge, Universitat Bayreuth, Bayreuth
Lianhong Gu, University of California, Berkeley
Richard Olson, Oak Ridge National Laboratory
David Hollinger, USDA Forest Service, Durham
Steve Running, University of Montana, Missoula
Peter Anthoni, Oregon State University, Corvallis
Ch. Bernhofer, Technische Universitat Dresden
Kenneth Davis, The Pennsylvania State University
Robert Evans, USDA Forest Service, Durham
Jose Fuente, University of Virginia, Charlottesville
Allen Goldstein, University of California, Berkeley
Gabriel Katul, Duke University, Durham
Beverly Law, Oregon State University, Corvallis
Xuhui Lee, Yale University, New HavenFollow
Yadvinder Malhi, University of Edinburgh, Edinburgh
Tilden Meyers, NOAA/Atrnospheric Turbulence and Diffusion Division
William Munge, Harvard University, Cambridge
Walt Oechel, San Diego State University
K.T. Paw U, University of California, Davis
Kim Pilegaard, Risoe National Laboratory, Roskilde
H.P. Schmid, Indiana University, Bloomington
Riccardo Valentini, Universita de Tuscia, Viterbo
Shashi Verma, University of Nebraska - LincolnFollow
Timo Vesala, University of Helsinki, Helsinki
Kell Wilson, NOAA/Atrnospheric Turbulence and Diffusion Division
Steve Wofsy, Harvard University, Cambridge

Date of this Version

2001

Citation

2001 American Meteorological Society

Comments

Vol. 82, No.11 , November 2001

Bulletin of the American Meteorological Society 2415-2434

Abstract

FLUXNET is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. At present over 140 sites are operating on a long-term and continuous basis. Vegetation under study includes temperate conifer and broadleaved (deciduous and evergreen) forests, tropical and boreal forests, crops, grasslands, chaparral, wetlands, and tundra. Sites exist on five continents and their latitudinal distribution ranges from 70°N to 30°S.

FLUXNET has several primary functions. First, it provides infrastructure for compiling, archiving, and distributing carbon, water, and energy flux measurement, and meteorological, plant, and soil data to the science community. (Data and site information are available online at the FLUXNET Web site, http://www-eosdis.ornl.gov/FLUXNET/.) Second, the project supports calibration and flux intercomparison activities. This activity ensures that data from the regional networks are intercomparable. And third, FLUXNET supports the synthesis, discussion, and communication of ideas and data by supporting project scientists, workshops, and visiting scientists. The overarching goal is to provide information for validating computations of net primary productivity, evaporation, and energy absorption that are being generated by sensors mounted on the NASA Terra satellite.

Data being compiled by FLUXNET are being used to quantify and compare magnitudes and dynamics of annual ecosystem carbon and water balances, to quantify the response of stand-scale carbon dioxide and water vapor flux densities to controlling biotic and abiotic factors, and to validate a hierarchy of soil-plant-atmosphere trace gas exchange models. Findings so far include 1) net C02 exchange of temperate broadleaved forests increases by about 5.7 g C m~2 day-1 for each additional day that the growing season is extended; 2) the sensitivity of net ecosystem C02 exchange to sunlight doubles if the sky is cloudy rather than clear; 3) the spectrum of C02 flux density exhibits peaks at timescales of days, weeks, and years, and a spectral gap exists at the month timescale; 4) the optimal temperature of net C02 exchange varies with mean summer temperature; and 5) stand age affects carbon dioxide and water vapor flux densities.