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Biosphere-atmosphere exchange of CO2 in relation to climate: a cross-biome analysis across multiple time scales
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 (PDF, 1936 KB) Discussion Paper (BGD)
Citation: Stoy, P. C., Richardson, A. D., Baldocchi, D. D., Katul, G. G., Stanovick, J., Mahecha, M. D., Reichstein, M., Detto, M., Law, B. E., Wohlfahrt, G., Arriga, N., Campos, J., McCaughey, J. H., Montagnani, L., Paw U, K. T., Sevanto, S., and Williams, M.: Biosphere-atmosphere exchange of CO2 in relation to climate: a cross-biome analysis across multiple time scales, Biogeosciences, 6, 2297-2312, 2009. Bibtex EndNote Reference Manager
