Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 6 10 2009 10.5194/bg-6-2297-2009 http://www.biogeosciences.net/6/2297/2009/ http://www.biogeosciences.net/6/2297/2009/bg-6-2297-2009.html http://www.biogeosciences.net/6/2297/2009/bg-6-2297-2009.pdf 2297 2312 2009-10-30 Biosphere-atmosphere exchange of CO₂ in relation to climate: a cross-biome analysis across multiple time scales P. C. Stoy paul.stoy@ed.ac.uk A. D. Richardson D. D. Baldocchi G. G. Katul J. Stanovick M. D. Mahecha M. Reichstein M. Detto B. E. Law G. Wohlfahrt N. Arriga J. Campos J. H. McCaughey L. Montagnani K. T. Paw U S. Sevanto M. Williams School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, UK Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717-3120, USA Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, USA Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708, USA USDA Forest Service, Northern Research Station, Newtown Square, PA 19073, USA Max Planck Institute for Biogeochemistry, P.O. Box 10 01 64, 07701 Jena, Germany Department of Environmental Sciences, ETH, 8092 Zürich, Switzerland Department of Forest Science, Oregon State University, USA Institut für Ökologie, Universität Innsbruck, Austria Department of Forest Science and Environment, University of Tuscia, 01100 Viterbo, Italy Instituto Nacional de Pesquisas da Amazônia – INPA, Manaus, Brasil Department of Geography, Queen's University, Canada Forest Service and Agency for the Environment, Autonomous Province of Bolzano, Bolzano, Italy University of Bolzano/Bozen, Bolzano, Italy Department of Land, Air, and Water Resources, University of California, Davis, USA Department of Physics, P.O. Box 64, 00014 University of Helsinki, Finland 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. Adair, E. C., Parton, W. J., Del Grosso, S. J., Silver, W. L., Harmon, M. E., Hall, S. A., Burke, I. C., and Hart, S. C.: Simple three-pool model accurately describes patterns of long-term litter decomposition in diverse climates, Glob. Change Biol., 14, 2636–2660, 2008. Agarwal, D., Baldocchi, D., Boden, T., Cook, B. D., Frank, D., Goode, M., Gupchup, J., Holladay, S., Humphrey, M., van Ingen, C., Jackson, B., Papale, D., Reichstein, M., Rodriguez, M., Ryu, Y., Vargas, R., Wilson, B., and Li, N.: Creating and accessing the global fluxnet data set, Eos Trans. AGU, 88, Abstract B33E-1657, 2007. Allen, M. R. and Smith, L. A.: Monte Carlo SSA: detecting irregular oscillations in the presence of colored noise, J. Climate, 9, 3373–3404, 1996. Arnone, J. A. I., Verburg, P. S. J., Johnson, D. W., Larsen, J. D., Jasoni, R. L., Luccesi, A. J., Batts, C. M., von Nagy, C., Coulombe, W. G., Schorran, D. E., Buck, P. E., Braswell, B. H., Coleman, J. S., Sherry, R. A., Wallace, L. L., Luo, Y., and Schimel, D. S.: Prolonged supression of ecosystem carbon dioxide uptake after an anomalously warm year, Nature, 455, 383–386, 2008. Aubinet, M., Grelle, A., Ibrom, A., Rannik, Ãœ., Moncrieff, J., Foken, T., Kowalski, A. S., Martin, P. H., Berbigier, P., Bernhofer, C., Clement, R., Elbers, J., Granier, A., Grünwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snijders, W., Valentini, R., and Vesala, T.: Estimates of the annual net carbon and water exchange of forests: The EUROFLUX methodology, Adv. Ecol. Res., 30, 113–175, 2000. Baldocchi, D., Falge, E., Gu, L. H., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, C., Davis, K., Evans, R., Fuentes, J., Goldstein, A., Katul, G., Law, B., Lee, X. H., Malhi, Y., Meyers, T., Munger, W., Oechel, W., U, K. T. P., Pilegaard, K., Schmid, H. P., Valentini, R., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: FLUXNET: A new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities, B. Am. Meteorol. Soc., 82, 2415–2434, 2001a. Baldocchi, D., Falge, E., and Wilson, K.: A spectral analysis of biosphere-atmosphere trace gas flux densities and meteorological variables across hour to multi-year time scales, Agr. Forest Meteorol., 107, 1–27, 2001b. Baldocchi, D. D. and Wilson, K. B.: Modeling CO₂ and water vapor exchange of a temperate broadleaved forest across hourly to decadal time scales, Ecol. Model., 142, 155–184, 2001. Baldocchi, D. D.: "Breathing" of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurements systems, Turner Review, Aust. J. Bot., 56, 1–26, 2008. Barbour, M. M., Hunt, J. E., Dungan, R. J., Turnbull, M. H., Brailsford, G. W., Farquhar, G. D., and Whitehead, D.: Variation in the degree of coupling between $\delta^13$C of phloem sap and ecosystem respiration in two mature Nothofagus forests, New Phytol., 166, 497–512, 2005. Battle, M., Bender, M. L., Tans, P. P., White, J. W. C., Ellis, J. T., Conway, T., and Francey, R. J.: Global carbon sinks and their variability inferred from atmospheric O₂ and $^13$C, Science, 287, 2467–2470, 2000. Braswell, B. H., Sacks, W. J., Linder, E., and Schimel, D. S.: Estimating diurnal to annual ecosystem parameters by synthesis of a carbon flux model with eddy covariance net ecosystem exchange observations, Glob. Change Biol., 11, 335–355, 2005. Canadell, J. G., Le Quere, C., Raupach, M. R., Field, C. B., Buitenhuis, E. T., Ciais, P., Conway, T. J., Gillett, N. P., Houghton, R. A., and Marland, G.: Contributions to accelerating atmospheric CO₂ growth from economic activity, carbon intensity, and efficiency of natural sinks, P. Natl. Acad. Sci. USA, 104, 18353–18354, 2007. Carvalhais, N., Reichstein, M., Seixas, J., Collatz, G. J., Pereira, J. S., Berbigier, P ., Carrara, A., Granier, A., Montagnani, L., Papale, D., Rambal, S., Sanz, M. J., and Valentini, R.: Implications of the carbon cycle steady state assumption for biogeochemical modeling performance and inverse parameter retrieval, Global Biogeochem. Cy., 22, GB2007, doi:10.1029/2007GB003033, 2008. Cava, D., Giostra, U., Siqueira, M. B. S., and Katul, G. G.: Organized motion and radiative perturbations in the nocturnal canopy sublayer above an even-aged pine forest, Bound.-Lay. Meteorol., 112, 129–157, 2004. Chapin III, F. S., Sturm, M., Serreze, M. C., McFadden, J. P., Key, J. R., Lloyd, A. H., McGuire, A. D., Rupp, T. S., Lynch, A. H., Schimel, J. P., Beringer, J., Chapman, W. L., Epstein, H. E., Euskirchen, E. S., Hinzman, L. D., Jia, G., Ping, C.-L., Tape, K. D., Thompson, C. D. C., Walker, D. A., and Welker, J. M.: Role of land-surface changes in arctic summer warming, Science, 310, 657–660, 2005. Ciais, P., Reichstein, M., Viovy, N., Granier, A., Ogée, J., Allard, V., Aubinet, M., Buchmann, N., Bernhofer, C., Carrara, A., Chevallier, F., de Noblet, N., Friend, A. D., Friedlingstein, P., Grünwald, T., Heinesch, B., Keronen, P., Knohl, A., Krinner, G., Lousteau, D., Manca, G., Matteucci, G., Miglietta, F., Ourcival, J. M., Papale, D., Pilegaard, K., Rambal, S., Seufert, G., Soussana, J. F., Sanz, M. J., Schulze, E. D., Vesala, T., and Valentini, R.: Europe-wide reduction in primary productivity caused by the heat and drought in 2003, Nature, 437, 529–533, 2005. Cook, B. D., Holladay, S., Santhana-Vannan, S. K., Pan, J. Y., Jackson, B., and Wilson, B.: FLUXNET: Data from a global network of eddy-covariance flux towers, Eos Trans. AGU, 88, Fall Meet. Suppl., Abstract B33E–1656, 2007. Curiel Yuste, J., Janssens, I. A., Carrara, A., and Ceulemans, R.: Annual Q$_10$ of soil respiration reflects plant phenological patterns as well as temperature sensitivity, Glob. Change Biol., 10, 161–169, 2004. Daly, E., and Porporato, A.: A review of soil moisture dynamics: from rainfall infiltration to ecosystem response, Environ. Eng. Sci., 22, 9–24, 2005. Daubechies, I.: Ten lectures on wavelets, SIAM: Society for Industrial and Applied Mathematics, 377~pp., 1992. Davidson, E. A., and Janssens, I. A.: Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature, 440, 165–173, 2006. Delpierre, N., Soudani, K., François, C., Köstner, B., Pontailler, J.-Y., Nikinmaa, E., Misson, L., Aubinet, M., Bernhofer, C., Granier, A., T., G., Heinesch, B., Longdoz, B., Ourcival, J.-M., Rambal, S., Vesala, T., and E., D.: Exceptional carbon uptake in european forests during the warm spring of 2007: a data-model analysis, Glob. Change Biol., 15, 1455–1474, 2009. Dengel S., Aeby, D., Grace, J.: A relationship between galactic cosmic radiation and tree rings, New Phytol., 184, 545–551, doi:10.1111/j.1469-8137.2009.03026.x, 2009. Drake, J., Stoy, P. C., Jackson, R. B., and DeLucia, E. H: Fine root respiration in a loblolly pine (\textitPinus taeda) forest: Proximal limits, temperature dependence, and dynamic coupling with canopy photosynthesis, Plant Cell Environ., 31, 1663–1672, 2008. Dunn, D. C. and Morrison, J. F.: Analysis of the energy budget in turbulent channel flow using orthogonal wavelets, Comput. Fluids, 34, 199–224, 2005. Ellsworth, D. S.: CO₂ enrichment in a maturing pine forest: are CO₂ exchange and water status in the canopy affected?, Plant Cell Environ., 22, 461–472, 1999. Falge, E., Baldocchi, D., Olson, R., Anthoni, P., Aubinet, M., Bernhofer, C., Burba, G., Ceulemans, R., Clement, R., Dolman, H., Granier, A., Gross, P., Grünwald, T., Hollinger, D., Jensen, N. O., Katul, G., Keronen, P., Kowalski, A., Lai, C. T., Law, B. E., Meyers, T., Moncrieff, J., Moors, E., Munger, J. W., Pilegaard, K., Rannik, Ãœ., Rebmann, C., Suyker, A., Tenhunen, J., Tu, K., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: Gap filling strategies for defensible annual sums of net ecosystem exchange, Agr. Forest Meteorol., 107, 43–69, 2001. Fraedrich, K. and Larnder, C.: Scaling regimes of composite rainfall time series, Tellus A, 45, 289–298, 1993. Frich, P., Alexander, L. V., Della-Marta, P., Gleason, B., Haylock, M., Klein Tank, A. M. G., and Peterson, T.: Observed coherent changes in climatic extremes during the second half of the twentieth century, Clim. Res., 19, 193–212, 2002. Friedlingstein, P., Cox, P., Betts, R. A., Bopp, L., von Blow, W., Brovkin, V., Cadule, P., Doney, S. C., Eby, M., Fung, I. Y., Bala, G., John, J., Jones, C. D., Joos, F., Kato, T., Kawamiya, M., Knorr, W., Lindsay, K., Matthews, H. D., Raddatz, T., Rayner, P. J., Reick, C., Roeckner, E., Schnitzler, K.-G., Schnur, R., Strassmann, K., Weaver, A. J., Yoshikawa, C., and Zeng, N.: Climate-carbon cycle feedback analysis: results from the C4MIP model intercomparison, J. Climate, 19, 3337–3353, 2006. Gilman, D. L., Fuglister, F. J., and Mitchell Jr., J. M.: On the power spectrum of "red noise", J. Atmos. Sci., 20, 182–184, 1963. Granier, A., Reichstein, M., Breda, N., Janssens, I. A., Falge, E., Ciais, P., Grünwald, T., Aubinet, M., Berbigier, P., Buchmann, N., Facini, O., Grassi, G., Heinesch, B., Ilvesniemi, H., Keronen, P., Knohl, A., Kostner, B., Lagergren, F., Lindroth, A., Longdoz, B., Loustau, D., Mateus, J., Montagnani, L., Nys, C., Moors, E., Papale, D., Peiffer, M., Pilegaard, K., Pita, G., Pumpanen, J., Rambal, S., Rebmann, C., Rodrigues, A., Seufert, G., Tenhunen, J., Vesala, T., and Wang, Q.: Evidence for soil water control on carbon dynamics in European forests during the extremly dry year: 2003, Agr. Forest Meteorol., 143, 123–145, 2007. Granier, A., Breda, N., Longdoz, B., Gross, P., and Ngao, J.: Ten years of fluxes and stand growth in a young beech forest at Hesse, North-eastern France, Ann. Forest Sci., 65, 704, doi:10.1051/forest:2008052, 2008. Grinsted, A., Moore, J. C., and Jevrejeva, S.: Application of the cross wavelet transform and wavelet coherence to geophysical time series, Nonlin. Processes Geophys., 11, 561–566, 2004. Grünwald, T. and Bernhofer, C.: A decade of carbon, water and energy flux measurements of an old spruce forest at the Anchor Station Tharandt, Tellus B, 59, 387–396, 2007. Hanson, P. J., Amthor, J. S., Wullschleger, S. D., Wilson, K. F., Grant, R. F., Hartley, A., Hui, D. F., Hunt, E. R. J., Johnson, D. W., Kimball, J. S., King, A. W., Y., L., McNulty, S. G., Sun, G., Thornton, P. E., Wang, S., Williams, M., Baldocchi, D. D., and Cushman, R. M.: Oak forest carbon and water simulations: model intercomparisons and evaluations against independent data., Ecol. Monogr., 74, 443–489, 2004. Hibbard, K., Law, B. E., Reichstein, M., Sulzman, J., Aubinet, M., Baldocchi, D., Bernhofer, C., Bolstad, P., Bosc, A., Campbell, J., Cheng, Y., Curiel Yuste, J., Curtis, P., Davidson, E. A., Epron, D., Granier, A., Grünwald, T., Hollinger, D., Janssens, I., Longdoz, B., Loustau, D., Martin, J., Monson, R., Oechel, W., Pippen, J., Ryel, R., Savage, K., Scott-Denton, L., Subke, J.-A., Tang, J., Tenhunen, J., Turcu, V., and Vogel, C. S.: An analysis of soil respiration across northern hemisphere temperate ecosystems, Biogeochemistry, 73, 29–70, 2005. Högberg, P., Nordgren, A., Buchmann, N., Taylor, A. F. S., Ekblad, A., Högberg, M. N., Nyberg, G., Ottoson-Löfvenius, M., and Read, D. J.: Large-scale forest girdling shows that current photosynthesis drives soil respiration, Nature, 411, 789–792, 2001. Houghton, R. A.: Interannual variability in the global carbon cycle, J. Geophys. Res.-Atmos., 105, 20121–20130, 2000. Irvine, J., Law, B. E., Martin, J., and Vickers, D.: Interannual variation in soil CO₂ efflux and the response of root respiration to climate and canopy gas exchange in mature ponderosa pine, Glob. Change Biol., 14, 2848–2859, 2008. Janssens, I. A., Lankreijer, H., Matteucci, G., Kowalski, A. S., Buchmann, N., Epron, D., Pilegaard, K., Kutsch, W., Longdoz, B., Grünwald, T., Montagnani, L., Dore, S., Rebmann, C., Moors, E. J., Grelle, A., Rannik, Ãœ., Morgenstern, K., Oltchev, S., Clement, R., Gudmundsson, J., Minerbi, S., Berbigier, P., Ibrom, A., Moncrieff, J., Aubinet, M., Bernhofer, C., Jensen, N. O., Vesala, T., Granier, A., Schulze, E. D., Lindroth, A., Dolman, A. J., Jarvis, P. G., Ceulemans, R., and Valentini, R.: Productivity overshadows temperature in determining soil and ecosystem respiration across European forests, Glob. Change Biol., 7, 269–278, 2001. Jarvis P. G.: The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field, Philos. T. Roy. Soc. London B., 273, 593–610, 1976. Juang, J.-Y., Katul, G. G., Siqueira, M. B. S., Stoy, P. C., and McCarthy, H. R.: Investigating a hierarchy of eulerian closure models for scalar transfer inside forested canopies, Bound.-Lay. Meteorol., 128, 1–32, 2008. Jung, M., Verstraete, M., Gobron, M., Reichstein, M., Papale, D., Bondeau, A., Robustelli, M., and Pinty, B.: Diagnostic assessment of European gross primary production, Glob. Change Biol., 14, 2349–2364, 2008. Kato, T. and Tang, Y.: Spatial variability and major controlling factors of CO₂ sink strength in Asian terrestrial ecosystems: evidence from eddy covariance data, Glob. Change Biol., 14, 2333–2348, 2008. Katul, G., Leuning, R., and Oren, R.: Relationship between plant hydraulic and biochemical properties derived from a steady-state coupled water and carbon transport model, Plant Cell Environ., 26, 339–350, 2003. Katul, G. G. and Parlange, M. B.: On the active role of temperature in surface layer turbulence, J. Atmos. Sci., 51, 2181–2195, 1994. Katul, G. G. and Parlange, M. B.: Analysis of land surface heat fluxes using the orthonormal wavelet approach, Water Resour. Res., 31, 2743–2749, 1995. Katul, G. G., Lai, C.-T., Schäfer, K. V. R., Vidakovic, B., Albertson, J. D., Ellsworth, D. S., and Oren, R.: Multiscale analysis of vegetation surface fluxes: from seconds to years, Adv. Water Resour., 24, 1119–1132, 2001. Katul, G. G., Porporato, A., Daly, E., Oishi, A. C., Kim, H.-S., Stoy, P. C., Juang, J.-Y., and Siqueira, M. B. S.: On the spectrum of soil moisture in a shallow-rooted uniform pine forest: from hourly to inter-annual time scales, Water Resour. Res., 43, W05428, doi:10.1029/2006WR005356, 2007. Lasslop, G., Reichstein, M., Papale, D., Richardson, A. D., Arneth, A., Barr, A. G., Stoy, P. C., and Wohlfahrt, G.: Separation of net ecosystem exchange into assimilation and respiration using a light response curve approach: critical issues and global evaluation Glob. Change Biol., doi:10.1111/j.1365-2486.2009.02041.x, in press, 2009. Law, B. E., Falge, E., Gu, L., Baldocchi, D. D., Bakwin, P., Berbigier, P., Davis, K., Dolman, A. J., Falk, M., Fuentes, J. D., Goldstein, A., Granier, A., Grelle, A., Hollinger, D., Janssens, I. A., Jarvis, P., Jensen, N. O., Katul, G., Mahli, Y., Matteucci, G., Meyers, T., Monson, R., Munger, W., Oechel, W., Olson, R., Pilegaard, K., Paw U, K. T., Thorgeirsson, H., Valentini, R., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation, Agr. Forest Meteorol., 113, 97–120, 2002. Lloyd, J. and Taylor, J. A.: On the temperature dependence of soil respiration, Funct. Ecol., 8, 315–323, 1994. Luyssaert, S., Schulze, E.-D., Börner, A., Knohl, A., Hessenmöller, D., Law, B.E., Ciais, P., and Grace, J.: Old-growth forests as global carbon sinks, Nature, 411, 213–215, 2008. Mahecha, M. D., Reichstein, M., Lange, H., Carvalhais, N., Bernhofer, C., Grünwald, T., Papale, D., and Seufert, G.: Characterizing ecosystem-atmosphere interactions from short to interannual time scales, Biogeosciences, 4, 743–758, 2007. Moffat, A. M., Papale, D., Reichstein, M., Hollinger, D. Y., Richardson, A. D., Barr, A. G., Beckstein, C., Braswell, B. H., Churkina, G., Desai, A. R., Falge, E., Gove, J. H., Heimann, M., Hui, D., Jarvis, A. J., Kattge, J., Noormets, A., and Stauch, V. J.: Comprehensive comparison of gap-filling techniques for eddy covariance net carbon fluxes, Agr. Forest Meteorol., 147, 209–232, 2007. Odum, E. P.: The strategy of ecosystem development, Science, 164, 262–270, 1969. Oren, R., Hsieh, C. I., Stoy, P. C., Albertson, J. D., McCarthy, H. R., Harrell, P., and Katul, G. G.: Estimating the uncertainty in annual net ecosystem carbon exchange: spatial variation in turbulent fluxes and sampling errors in eddy-covariance measurements, Glob. Change Biol., 12, 883–896, 2006. Owen, K. E., Tenhunen, J., Reichstein, M., Wang, Q., Falge, E., Geyer, R., Xiao, X., Stoy, P., Ammann, C., Arain, A., Aubinet, M., Aurela, M., Bernhofer, C., Chojnicki, B., Granier, A., Grünwald, T., Hadley, J., Heinesch, B., Hollinger, D., Knohl, A., Kutsch, W., Lohila, A., Meyers, T., Moors, E., Moureaux, C., Pilegaard, K., Saigusa, N., Verma, S., Vesala, T., and Vogel, C.: Linking flux network measurements to continental scale simulations: ecosystem CO₂ exchange capacity under non-water-stressed conditions, Glob. Change Biol., 13, 734–760, 2007. Palmroth, S., Maier, C. A., McCarthy, H. R., Oishi, A. C., Kim, H.-S., Johnsen, K. H., Katul, G. G., and Oren, R.: Contrasting responses to drought of the forest floor CO₂ efflux in a loblolly pine plantation and a nearby oak-hickory forest, Glob. Change Biol., 11, 421–434, 2005. Papale, D., Reichstein, M., Aubinet, M., Canfora, E., Bernhofer, C., Kutsch, W., Longdoz, B., Rambal, S., Valentini, R., Vesala, T., and Yakir, D.: Towards a standardized processing of Net Ecosystem Exchange measured with eddy covariance technique: algorithms and uncertainty estimation, Biogeosciences, 3, 571–583, 2006. Parton, W. J., Schimel, D. S., Cole, C. V., and Ojima, D. S.: Analysis of factors controlling soil organic levels of grasslands in the Great Plains, Soil Sci. Soc. Am. J., 51, 1173–1179, 1987. Peters, O., Hertlein, C., and Christensen, K.: A complexity view of rainfall, Phys. Rev. Lett., 88, 018701–018704, 2002. Porporato, A., D'Odorico, P., Laio, F., Ridolfi, L., and Rodriguez-Iturbe, I.: Ecohydrology of water-controlled ecosystems, Adv. Water Resour., 25, 1335–1348, 2002. Potter, C. S., Klooster, S. A., Steinbach, M., Tan, P., Kumar, V., Shekhar, S., Nemani, R., and Myneni, R. B.: Global teleconnections of climate to terrestrial carbon flux, J Geophys. Res., 108(D17), 4556, doi:10.1029/2002JD002979, 2003. Potter, C. S., Klooster, S. A., Tan, P., Steinbach, M., Kumar, V., and Genovese, V.: Variability in terrestrial carbon sinks over two decades: Part 2 - Eurasia, Global Planet. Change, 49, 177–186, 2005. Qian, H., Renu, J., and Zeng, N.: Response of the terrestrial carbon cycle to the El Niño-Southern Oscillation, Tellus B, 60, 537–550, 2008. Reichstein, M., Tenhunen, J., Roupsard, O., Ourcival, J.-M., Rambal, S., Miglietta, F., Peressotti, A., Pecchiari, M., Tirone, G., and Valentini, R.: Inverse modeling of seasonal drought effects on canopy CO₂/H₂O exchange in three Mediterranean ecosystems, J Geophys. Res., 108(D23), 4726, doi:10.1029/2003JD003430, 2003. Reichstein, M., Falge, E., Baldocchi, D., Papale, D., Aubinet, M., Berbigier, P., Bernhofer, C., Buchmann, N., Gilmanov, T. G., Granier, A., Grünwald, T., Havránková, K., Ilvesniemi, H., Janous, D., Knohl, A., Laurila, T., Lohila, A., Loustau, D., Matteucci, G., Meyers, T., Miglietta, F., Ourcival, J.-M., Pumpanen, J., Rambal, S., Rotenberg, E., Sanz, M., Tenhunen, J., Seufert, G., Vaccari, F., Vesala, T., Yakier, D., and Valentini, R.: On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm, Glob. Change Biol., 11, 1424–1439, 2005. Reichstein, M., Ciais, P., Papale, D., Valentini, R., Running, S., Viovy, N., Cramer, W., Granier, A., Ogee, J., Allard, V., Aubinet, M., Bernhofer, C., Buchmann, N., Carrara, A., Grünwald, T., Heimann, M., Heinesch, B., Knohl, A., Kutsch, W., Loustau, D., Manca, G., Matteucci, G., Miglietta, F., Ourcival, J. M., Pilegaard, K., Pumpanen, J., Rambal, S., Schaphoff, S., Seufert, G., Soussana, J. F., Sanz, M. J., Vesala, T., and Zhao, M.: Reduction of ecosystem productivity and respiration during the European summer 2003 climate anomaly: a joint flux tower, remote sensing and modelling analysis, Glob. Change Biol., 13, 634–651, 2007a. Reichstein, M., Papale, D., Valentini, R., Aubinet, M., Bernhofer, C., Knohl, A., Laurila, T., Lindroth, A., Moors, E., Pilegaard, K., and Seufert, G.: Determinants of terrestrial ecosystem carbon balance inferred from European eddy covariance flux sites, Geophys. Res. Lett., 34, L01402, doi:10.1029/2006GL027780, 2007b. Richardson, A. D., Hollinger, D. Y., Burba, G. G., Davis, K. J., Flanagan, L. B., Katul, G. G., Munger, J. W., Ricciuto, D. M., Stoy, P. C., Suyker, A. E., Verma, S. B., and Wofsy, S. C.: A multi-site analysis of random error in tower-based measurements of carbon and energy fluxes, Agr. Forest Meteorol., 136, 1–18, 2006. Richardson, A. D., Hollinger, D. Y., Aber, J. D., Ollinger, S. V., and Braswell, B. H.: Environmental variation is directly responsible for short- but not long-term variation in forest-atmosphere carbon exchange, Glob. Change Biol., 13, 788–803, 2007. Richardson, A. D., Mahecha, M. D., Falge, E., Kattge, J., Moffat, A. M., Papale, D., Reichstein, M., Stauch, V. J., Braswell, B. H., Churkina, G., Kruijt, B., and Hollinger, D. Y.: Statistical properties of random CO₂ flux measurement uncertainty inferred from model residuals, Agr. Forest Meteorol., 148, 38–50, 2008. Rigozo, N. R., Nordemann, D. J. R., da Silva, H. E., Echer, M. P. d. S., and Echer, E.: Solar and climate signal records in tree ring width from Chile (AD 1587–1994), Planet. Space Sci., 55, 158–164, 2007. Rocha, A. V., Goulden, M. L., Dunn, A. L., and Wofsy, S. C.: On linking interannual tree ring variability with observations of whole-forest CO₂ flux, Glob. Change Biol., 12, 1378–1389, 2006. Ryan, M. G. and Law, B. E.: Interpreting, measuring, and modeling soil respiration, Biogeochemistry, 73, 3–27, 2005. Saito, M. and Asunama, J.: Eddy covariance calculation revisited with wavelet cospectra, Sola, 4, 49–52, 2008. Scanlon, T. M. and Albertson, J. D.: Turbulent transport of carbon dioxide and water within vegetation canopies during unstable conditions: identification of episodes using wavelet analysis, J. Geophys. Res.-Atmos., 106, 7251–7262, 2001. Schär, C., Vidale, P. L., Lüthi, D., Frei, C., Häberli, C., and Liniger, M. A.: The role of increasing temperature variability in European summer heatwaves, Nature, 427, 332–336, 2004. Scheffer, M., Carpenter, S. R., Foley, J. A., Folke, C., and Walker, B. H.: Catastrophic shifts in ecosystems, Nature, 413 591–596, 2001. Siqueira, M. B. S., Katul, G. G., Sampson, D. A., Stoy, P. C., Juang, J.-Y., McCarthy, H. R., and Oren, R.: Multi-scale model inter-comparisons of CO₂ and H₂O exchange rates in a maturing southeastern U.S. pine forest, Glob. Change Biol., 12, 1189–1207, 2006. Stoy, P. C., Katul, G. G., Siqueira, M. B. S., Juang, J.-Y., McCarthy, H. R., Kim, H.-S., Oishi, A. C., and Oren, R.: Variability in net ecosystem exchange from hourly to inter-annual time scales at adjacent pine and hardwood forests: a wavelet analysis, Tree Physiol., 25, 887–902, 2005. Stoy, P. C., Palmroth, S., Oishi, A. C., Siqueira, M. B. S., Juang, J.-Y., Novick, K. A., Ward, E. J., Katul, G. G., and Oren, R.: Are ecosystem carbon inputs and outputs coupled at short time scales? A case study from adjacent pine and hardwood forests using impulse-response analysis, Plant Cell Environ., 30, 700–710, 2007. Stoy, P. C., Katul, G. G., Siqueira, M. B. S., Juang, J.-Y., Novick, K., McCarthy, H. R., Oishi, A. C., and Oren, R.: Role of vegetation in determining carbon sequestration along ecological succession in the southeastern United States, Global Change Biol., 14, 1409–1427, 2008. Taneva, L., Pippen, J. S., Schlesinger, W. H., and González-Meler, M. A.: The turnover of carbon pools contributing to soil CO₂ and soil respiration in a temperate forest exposed to elevated CO₂ concentration, Glob. Change Biol., 12, 983–994, 2006. Tang, J., Baldocchi, D., and Xu, L.: Tree photosynthesis modulates soil respiration on a diurnal time scale, Glob. Change Biol., 11, 1298–1304, 2005. Thomas, C. K., Law, B. E., Irvine, J., Martin, J. G., Pettijohn, J. C., and Davis, K. J.: Seasonal hydrology explains inter-annual and seasonal variation in carbon and water exchange in a semi-arid mature Ponderosa Pine forest in Central Oregon, J. Geophys. Res.- Biogeosciences, doi:10.1029/2009JG001010, in press, 2009. Torrence, C. and Compo, G. P.: A practical guide to wavelet analysis, B. Am. Meteorol. Soc., 79, 61–78, 1998. Urbanski, S. P., Barford, C., Wofsy, S., Kucharik, C. J., Pyle, E. H., Budney, J., McKain, K., Fitzjarrald, D., Czikowsky, M. J., and Munger, J. W.: Factors controlling CO₂ exchange on timescales from hourly to decadal at Harvard Forest, J. Geophys. Res., 112, G02020, doi:10.1029/2006JG000293, 2007. Valentini, R., Matteucci, G., Dolman, A. J., Schulze, E. D., Rebmann, C., Moors, E. J., Granier, A., Gross, P., Jensen, N. O., Pilegaard, K., Lindroth, A., Grelle, A., Bernhofer, C., Grünwald, T., Aubinet, M., Ceulemans, R., Kowalski, A. S., Vesala, T., Rannik, Ãœ., Berbigier, P., Loustau, D., Guomundsson, J., Thorgeirsson, H., Ibrom, A., Morgenstern, K., Clement, R., Moncrieff, J., Montagnani, L., Minerbi, S., and Jarvis, P. G.: Respiration as the main determinant of carbon balance in European forests, Nature, 404, 861–865, 2000. Vickers, D., Thomas, C. K., Martin, J. G., and Law, B. E.: Self-correlation between assimilation and respiration resulting from flux partitioning of eddy-covariance CO₂ fluxes, Agr. Forest Meteorol., 149, 1552–1555, 2009. Williams, M., Richardson, A. D., Reichstein, M., Stoy, P. C., Peylin, P., Verbeeck, H., Carvalhais, N., Jung, M., Hollinger, D. Y., Kattge, J., Leuning, R., Luo, Y., Tomelleri, E., Trudinger, C. M., and Wang, Y.-P.: Improving land surface models with FLUXNET data, Biogeosciences, 6, 1341–1359, 2009. Wilson, K. B., Baldocchi, D. D., and Hanson, P. J.: Leaf age affects the seasonal pattern of photosynthetic capacity and net ecosystem exchange of carbon in a deciduous forest, Plant Cell Environ., 24, 571–583, 2001.