Articles | Volume 6, issue 10
Biogeosciences, 6, 2297–2312, 2009
Biogeosciences, 6, 2297–2312, 2009

  30 Oct 2009

30 Oct 2009

Biosphere-atmosphere exchange of CO2 in relation to climate: a cross-biome analysis across multiple time scales

P. C. Stoy1,2, A. D. Richardson3, D. D. Baldocchi4, G. G. Katul5, J. Stanovick6, M. D. Mahecha7,8, M. Reichstein7, M. Detto4, B. E. Law9, G. Wohlfahrt10, N. Arriga11, J. Campos12, J. H. McCaughey13, L. Montagnani14,15, K. T. Paw U16, S. Sevanto17, and M. Williams1 P. C. Stoy et al.
  • 1School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, UK
  • 2Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717-3120, USA
  • 3Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
  • 4Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, USA
  • 5Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708, USA
  • 6USDA Forest Service, Northern Research Station, Newtown Square, PA 19073, USA
  • 7Max Planck Institute for Biogeochemistry, P.O. Box 10 01 64, 07701 Jena, Germany
  • 8Department of Environmental Sciences, ETH, 8092 Zürich, Switzerland
  • 9Department of Forest Science, Oregon State University, USA
  • 10Institut für Ökologie, Universität Innsbruck, Austria
  • 11Department of Forest Science and Environment, University of Tuscia, 01100 Viterbo, Italy
  • 12Instituto Nacional de Pesquisas da Amazônia – INPA, Manaus, Brasil
  • 13Department of Geography, Queen's University, Canada
  • 14Forest Service and Agency for the Environment, Autonomous Province of Bolzano, Bolzano, Italy
  • 15University of Bolzano/Bozen, Bolzano, Italy
  • 16Department of Land, Air, and Water Resources, University of California, Davis, USA
  • 17Department of Physics, P.O. Box 64, 00014 University of Helsinki, Finland

Abstract. The net ecosystem exchange of CO2 (NEE) varies at time scales from seconds to years and longer via the response of its components, gross ecosystem productivity (GEP) and ecosystem respiration (RE), to physical and biological drivers. Quantifying the relationship between flux and climate at multiple time scales is necessary for a comprehensive understanding of the role of climate in the terrestrial carbon cycle. Orthonormal wavelet transformation (OWT) can quantify the strength of the interactions between gappy eddy covariance flux and micrometeorological measurements at multiple frequencies while expressing time series variance in few energetic wavelet coefficients, offering a low-dimensional view of the response of terrestrial carbon flux to climatic variability. The variability of NEE, GEP and RE, and their co-variability with dominant climatic drivers, are explored with nearly one thousand site-years of data from the FLUXNET global dataset consisting of 253 eddy covariance research sites. The NEE and GEP wavelet spectra were similar among plant functional types (PFT) at weekly and shorter time scales, but significant divergence appeared among PFT at the biweekly and longer time scales, at which NEE and GEP were relatively less variable than climate. The RE spectra rarely differed among PFT across time scales as expected. On average, RE spectra had greater low frequency (monthly to interannual) variability than NEE, GEP and climate. CANOAK ecosystem model simulations demonstrate that "multi-annual" spectral peaks in flux may emerge at low (4+ years) time scales. Biological responses to climate and other internal system dynamics, rather than direct ecosystem response to climate, provide the likely explanation for observed multi-annual variability, but data records must be lengthened and measurements of ecosystem state must be made, and made available, to disentangle the mechanisms responsible for low frequency patterns in ecosystem CO2 exchange.

Final-revised paper