Introduction

FLUXNET, a "network of regional networks," coordinates regional and global analysis of observations from micrometeorological tower sites (Figure 1). The flux tower sites use eddy covariance methods to measure the exchanges of carbon dioxide (CO2), water vapor, and energy between terrestrial ecosystems and the atmosphere.

At present over 650 tower sites are operated on a long-term and continuous basis (Figure 2). Vegetation under study includes temperate conifer and broadleaved (deciduous and evergreen) forests, tropical and boreal forests, crops, grasslands, chaparral, wetlands and tundra. Sites can be associated with regional or domain networks or can be unaffiliated. Flux towers operate on five continents and their latitudinal distribution ranges from 70 degrees north to 30 degrees south.

The FLUXNET database contains information about tower location and site characteristics as well as data availability (See FLUXNET Database). Eddy covariance data at 30-minute frequency are typically maintained, not by FLUXNET, but by individual towers or by networks to enable standardized data processing, gap-filling, and formats.

FLUXNET, which is a component of NASA's ORNL DAAC (Distributed Active Archive Center), has several primary functions:

  • provides infrastructure for a central database of site characteristic data (land cover, climate, meteorology, plant, and soil data);
  • maintains information about the availability of flux data along with links to the flux data at individual towers or at networks;
  • archives flux data associated with manuscripts (Chapin et al. 2002), workshops (Falge et al. 2005), as well as site characteristics and ancillary data about flux tower sites (Luyssaert et al. 2009);
  • compiles, archives, and distributes carbon, water and energy flux measurements for unaffiliated sites and others, as requested; and
  • provides information for evaluating remote sensing products, such as primary productivity, evaporation, albedo, and energy absorption.

In a related effort, the ORNL DAAC provides subsets of remote sensing products (MODIS Land Products) for an area 7 x 7 km around each flux tower in the FLUXNET collection. This information can be used as background site characteristic data, to examine ecosystem dynamics, to scale up the findings at tower sites, or to parameterize ecosystem models.

References

Chapin, F. S., III, W. Eugster, and J. P. McFadden. 2002. Arctic Tundra Flux Study in the Kuparuk River Basin (Alaska), 1994-1996. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/629.

Falge, E., M. Aubinet, P. Bakwin, D. Baldocchi, P. Berbigier, C. Bernhofer, A. Black, R. Ceulemans, A. Dolman, A. Goldstein, M. Goulden, A. Granier, D. Hollinger, P. Jarvis, N. Jensen, K. Pilegaard, G. Katul, P. Kyaw Tha Paw, B. Law, A. Lindroth, D. Loustau, Y. Mahli, R. Monson, P. Moncrieff, E. Moors, W. Munger, T. Meyers, W. Oechel, E. Schulze, H. Thorgeirsson, J. Tenhunen, R. Valentini, S. Verma, T. Vesala, and S. Wofsy. 2005. FLUXNET Marconi Conference Gap-Filled Flux and Meteorology Data, 1992-2000. Data set. Available on-line [http//www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/811.

Luyssaert, S., I. Inglima and M. Jung. 2009. Global Forest Ecosystem Structure and Function Data for Carbon Balance Research. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/949.

Relationship of tower sites, regional networks, and FLUXNET, the global network of regional networks.
Relationship of tower sites, regional networks, and FLUXNET, the global network of regional networks.

Distribution of tower sites within the global network of networks.
Distribution of tower sites within the global network of networks.