Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 6 2008 10.5194/bg-5-1625-2008 http://www.biogeosciences.net/5/1625/2008/ http://www.biogeosciences.net/5/1625/2008/bg-5-1625-2008.html http://www.biogeosciences.net/5/1625/2008/bg-5-1625-2008.pdf 1625 1639 2008-12-03 Assessing seasonality of biochemical CO2 exchange model parameters from micrometeorological flux observations at boreal coniferous forest T. Thum tea.thum@fmi.fi T. Aalto T. Laurila M. Aurela A. Lindroth T. Vesala Finnish Meteorological Institute, Climate Change Research, P.O. Box 503, 00101 Helsinki, Finland Lund University, Department of Physical Geography and Ecosystems Analysis, Sölvegatan 12, 223 62 Lund, Sweden University of Helsinki, Department of Physics, P.O. Box 64, 00014 University of Helsinki, Finland The seasonality of the NEE of the northern boreal coniferous forests was investigated by means of inversion modelling using eddy covariance data. Eddy covariance data was used to optimize the biochemical model parameters. Our study sites consisted of three Scots pine (l. Pinus sylvestris) forests and one Norway spruce (l. Picea abies) forest that were located in Finland and Sweden. We obtained temperature and seasonal dependence for the biochemical model parameters: the maximum rate of carboxylation (Vc(max)) and the maximum rate of electron transport (Jmax). Both of the parameters were optimized without assumptions about their mutual magnitude. The values obtained for the biochemical model parameters were similar at all the sites during summer time. To describe seasonality, different temperature fits were made for the spring, summer and autumn periods. During summer, average Jmax across the sites was 54.0 μmol m−2 s−1 (variance 31.2 μmol m−2 s−1) and Vc(max) was 12.0 μmol m−2 s−1 (variance 6.6 μmol m−2 s−1) at 17°C. The sensitivity of the model to LAI and atmospheric soil water stress was also studied. The impact of seasonality on annual GPP was 17% when only summertime parameterization was used throughout the year compared to seasonally changing parameterizations. Aalto, T.: Carbon dioxide exchange of Scots pine shoots as estimated by a biochemical model and cuvette field measurements, Silva Fenn., 32, 321–337, 1998. Aalto, T., Hari, P., and Vesala, T.: Comparison of an optimal stomatal regulation model and a biochemical model in explaining CO2 exchange in field conditions, Silva Fenn., 36, 615–623, 2002. Ainsworth, E. A. and Rogers, A.: The response of photosynthesis and stomatal conductance to rising [CO2]: mechanisms and environmental interactions, Plant, Cell Environ., 30, 258–270, 2007. Arneth, A., Lloyd, J., Shibistova, O., Sogachev, A., and Kolle, O.: Spring in the boreal environment: observations on pre- and post-melt energy and CO$_2 $fluxes in two central Siberian ecosystems, Boreal Environ. Res., 11, 311–328, 2006. Aurela, M.: Carbon dioxide exchange in subarctic ecosystems measured by a micrometeorological technique, Contributions, 51, Finnish Meteorological Institute, Helsinki, Finland, 132 pp., 2005. Ball, J. T., Woodrow, I. E., and Berry, J. A.: A model for predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions, in: I. Biggings (Ed.), Progress in photosynthesis research, Martinus Nijhoff Publishers, The Netherlands, Vol. IV, 221–224, 1987. Bergeron, O., Margolis, H. A., Black, T. A., Coursolle, C., Dunn, A. L., Barr, A. G., and Wofsy, S. C.: Comparison of carbon dioxide fluxes over three boreal black spruce forests in Canada, Global Change Biol., 13, 89-107, 2007. Bergh, J. and Linder, S.: Effects of soil warming during spring on photosynthetic recovery in boreal Norway spruce stands, Global Change Biol., 5, 245–253, 1999. Bergh, J., McMurtrie, R. E., and Linder, S.: Climatic factors controlling the productivity of Norway spruce: a model-based analysis, Forest Ecol. Manag., 110, 127–139, 1998. Brooks, A. and Farquhar, G. D.: Effect of temperature on the CO2/O2 specificity of ribulose 1,5-biphosphate carboxylase/oxygenase and the rate of respiration in the light, Planta, 165, 397–406, 1985. Dang, Q.-L., Margolis, H. A., and Collatz, G. J.: Parameterization and testing of a coupled photosynthesis-stomatal conductance model for boreal trees, Tree Phys., 18, 141–153, 1998. De Pury, D. G. G. and Farquhar, G. D.: Simple scaling of photosynthesis from leaves to canopies without the errors of big-leaf models, Plant Cell Environ., 20, 539–557, 1997. Ensminger, I., Sveshnikov, D., Campbell, D. A., Funk, C., Jansson, S., Lloyd, J., Shibistova, O., and Öquist, G.: Intermittent low temperatures constrain spring recovery of photosynthesis in boreal Scots pine forests, Global Change Biol., 10, 995–1008, 2004. Ensminger, I., Schmidt, L., and Lloyd, J.: Soil temperature and intermittent frost modulate the rate of recovery of photosynthesis in Scots pine under simulated spring conditions, New Phytol., 177, 428–442, 2008. Falge, E., Baldocchi, D., Tenhunen, J., Aubinet, M., Bakwin, P., Berbigier, P., Bernhofer, Chr., Burba, G., Clement, R., Davis, K. J., Elbers, J. A., Goldstein, A. H., Grelle, A., Granier, A., Gu$\eth$mundsson, J., Hollinger, D., Kowalski, A. S., Katul, G., Law, B. E., Malhi, Y., Meyers, T., Monson, R. K., Munger, J. W., Oechel, W., Paw U. K. T., Pilegaard, K., Rannik, Ü., Rebmann, C., Suyker, A., Valentini, R., Wilson, K., and Wofsy, S.: Seasonality of ecosystem respiration and gross primary production as derived from FLUXNET measurements, Agr. Forest Meteorol., 113, 53–74, 2002. Farquhar, G. D., and von Caemmerer, S.: Modelling of photosynthetic response to environmental conditions, in: Lange, O. L., Nobel, P. S., Osmond, C. B., and Ziegler, H. (eds.), Encyclopedia of Plant Physiology 12B, Berlin, Springer-Verlag, 550–587, 1982. Farquhar, G. D., von Caemmerer S., and Berry, J. A.: A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species, Planta, 149, 78–90, 1980. Finnish Meteorological Institute: Climatological Statistics in Finland 1961-1990, Supplement to the Meteological Yearbook of Finland, The Finnish Meteorological Institute, Helsinki, Finland, 125 pp., 1991. Grassi, G., Colom, M. R., and Minotta, G.: Effects of nutrient supply on photosynthetic acclimation and photoinhibition of one-year-old foliage of Picea abies, Physiol. Plantarum, 111, 245–254, 2001. Grelle, A., Lindroth, A., and Mölder, M.: Seasonal variation of boreal forest surface conductance and evaporation, Agr. Forest Meteorol., 98–99, 563–578, 1999. Han, Q., Kawasaki, T., Nakano, T., and Chaba, Y.: Spatial and seasonal variability of temperature responses of biochemical photosynthesis parameters and leaf nitrogen content within a Pinus densiflora crown, Tree Phys., 24, 737–744, 2004. Harley, P.C., and Baldocchi, D.: Scaling carbon dioxide and water vapour exchange from leaf to canopy in a deciduous forest. I. Leaf model parametrization, Plant Cell Environ., 18, 1146–1156, 1995. Harrison, R. G., Jones, C. D., and Hughes, J. K.: Competing roles of rising CO2 and climate change in the contemporary European carbon balance, Biogeosciences, 5, 1–10, online available at: http://www.biogeosciences.net/5/1/2008/, 2008. Hikosaka, K., Ishikawa, K., Borjigidai, A., Muller, O., and Onoda, Y.: Temperature acclimation of photosynthesis: mechanisms involved in the changes in temperature dependence of photosynthetic rate, J. Exp. Bot., 57, 291–302, 2006. Hollinger, D. Y., Aber, J., Dail, B., Davidson, E. A., Goltz, S. M., Hughes, H., Leclerc, M. Y., Lee, J. T., Richardson, A. D., Rodriguez, C., Scotts, N. A., Achuatavarier, D., and Walsh, J.: Spatial and temporal variability in forest atmosphere CO2 exchange, Global Change Biol., 10, 1689–1706, 2004. Janssens, I., Medlyn, B., Gielen, B., Laureysens, I., Jach, M. E., Van Hove, D., and Ceulemans, R.: Carbon budget of Pinus sylvestris saplings after four years of exposure to elevated atmospheric carbon dioxide concentration, Tree Phys., 25, 325–337, 2005. Juurola, E., Aalto, T., Thum, T., Vesala, T., and Hari, P.: Temperature dependence of leaf-level CO2 fixation: revising biochemical coefficients through analysis of leaf three-dimensional structure, New Phytol., 166, 205–216, 2005. Kattge, J. and Knorr, W.: Temperature acclimation in a biochemical model of photosynthesis: A reanalysis of data from 36 species, Plant Cell Environ., 30, 1176–1190, 2007. Knorr, W. and Kattge, J.: Inversion of terrestrial ecosystem model parameter values against eddy covariance measurements by Monte Carlo sampling, Global Change Biol., 11, 1333–1351, 2005. Kolari, P., Lappalainen, H. K., Hänninen, H., and Hari, P.: Relationship between temperature and the seasonal course of photosynthesis in Scots pine at northern timberline and in southern boreal zone, Tellus, 59B, 542–552, 2007. Kosugi, Y., Shibata, S., and Kobashi, S.: Parameterization of the CO2 and H2O gas exchange of several temperate deciduous broad-leaved trees at the leaf scale considering seasonal changes, Plant Cell Environ., 26, 285–301, 2003. Kosugi, Y. and Matsuo, N.: Seasonal fluctuations and temperature dependence of leaf gas exchange parameters of co-occurring evergreen and deciduous trees in a temperate broad-leaved forest, Tree Physiol., 26, 1173–1184, 2006. Kull, O. and Jarvis, P. G.: The role of nitrogen in a simple scheme to scale up photosynthesis from leaf to canopy, Plant, Cell Environ., 18, 1174–1182, 1995. Lagarias, J. C., Reeds, J. A., Wright, M. H., and Wright, P. E.: Convergence properties of the Nelder-Mead simplex method in low dimensions, SIAM J. Optimiz., 9, 112–147, 1998. Law, B. E., Falge, E., Gu, L., Baldocchi, 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. Lawrie, J. and Hearne, J.: Reducing model complexity via output sensitivity, Ecol. Model., 207, 137–144, 2007. Leuning, R.: Scaling to a common temperature improves the correlation between photosynthesis parameters $J_\rmmax$ and $V_\rmcmax$, J. Exp. Bot., 307, 345–347, 1997. Leuning, R.: Temperature dependence of two parameters in a photosynthesis model, Plant Cell Environ., 25, 1205–1210, 2002. Lindroth, A., Lagergren, F., Aurela, M., Bjarnadottir, B., Christensen, T., Dellwik, E., Grelle, Ibrom, A., Johansson, T., Lankreijer, H., Launiainen, S., Laurila, T., Mölder, M., Nikinmaa, E., Pilegaard, K., Sigurdsson, B. D., and Vesala, T.: Leaf area index is the principal scaling parameter for both gross photosynthesis and ecosystem respiration of Northern deciduous and coniferous forests, Tellus, B60, 129–142, doi:10.1111/j.1600-0889.2007.00330.x, 2008. Lloyd, J. and Taylor, J. A.: On the temperature dependence of soil respiration, Funct. Ecol., 8, 315–323, 1994. Lloyd, J., Wong, S. C., Styles, J. M., Batten, D., Priddle, R., Turnbull, C., and McConchie C. A.: Measuring and modelling whole-tree gas exchange, Aust. J. Plant Physiol., 22, 987–1000, 1995. Luomala, E.-M., Laitinen, K., Kellomäki, S., and Vapaavuori, E.: Variable photosynthetic acclimation in consecutive cohorts of Scots pine needles during 3 years of growth at elevated CO2 and elevated temperature, Plant, Cell and Environ., 26, 645–660, 2003. Luomala, E.-M., Laitinen, K., Sutinen, S., Kellomäki S., and Vapaavuori, E.: Stomatal density, anatomy and nutrient concentrations of Scots pine needles are affected by elevated CO2 and temperature, Plant, Cell Environ., 28, 733–749, 2005. Mäkelä, A., Pulkkinen, M., Kolari, P., Lagergren, F., Berbigier, P., Lindroth, A., Loustau, D., Nikinmaa, E., Vesala, T., and Hari, P.: Developing an empirical model of stand GPP with the LUE approach: analysis of eddy covariance data at five contrasting conifer sites in Europe, Global Change Biol., 14, 92–108, 2008. Markkanen, T., Rannik, Ü., Keronen, P., Suni, T., and Vesala, T.: Eddy covariance fluxes over a boreal Scots pine forest, Boreal Environ. Res., 6, 65–78, 2001. Medlyn, B. E., Badeck, F.-W, de Pury, D. G. G., Barton, C. V., Broadmeadow, M., Ceulemans, R., de Angelis, P., Forstreuter, M., Jach, M. E., Kellomäki, S., Laitat, E., Marek, M., Philippot, S., Rey, A., Strassemeyer, J., Laitinen, K., Liozon, R., Portier, B., Roberntz ,P., Wang, K. and Jarvis, P. G.: Effects of elevated [CO2] on photosynthesis in European forest species: a meta-analysis of model Parameters, Plant, Cell Environ., 22, 1475–1495, 1999. Medlyn, B. E., Dreyer, E., Ellsworth, D., Forstreuter, M., Harley, P. C., Kirschbaum, M. U. F., Le Roux, X., Montpied, P., Strassemeyer, J., Walcroft, A., Wang, K. and Loustau, D.: Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data, Plant, Cell Environ., 25, 1167–1179, 2002a. Medlyn, B. E., Loustau, D., and Delzon, S.: Temperature response of parameters of a biochemically based model of photosynthesis. I. Seasonal changes in mature maritime pine (Pinus Pinaster Ait.), Plant, Cell Environ., 25, 1155–1165, 2002b. Medlyn, B. E., Berbigier, P., Clement, R., Grelle, A., Loustau, D., Linder, S., Wingate, L., Jarvis, P. G., Sigurdsson, B. D., and McMurtrie, R. E.: Carbon balance of coniferous forests growing in contrasting climates: Model-based analysis, Agr. Forest Meteorol., 131, 97–124, 2005a. Medlyn, B. E., Robinson, A. P., Clement, R., and McMurtrie, R. E.: On the validation of models of forest CO2 exchange using eddy covariance data: some perils and pitfalls, Global Change Biol., 25, 839–857, 2005b. 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. Muukkonen, P.: Needle biomass turnover rates of Scots pine (\textitPinus sylvestris L.) derived from the needle-shed dynamics, Trees, 19, 273–279, 2005. Ogée, J., Brunet, Y., Loustau, D., Berbigier, P., and Delzon, S.: \textitMuSICA, a CO2, water and energy multilayer, multileaf pine forest model: evaluation from hourly to yearly time scales and sensitivity analysis, Global Change Biol., 9, 697–717, 2003. Pelkonen, P. and Hari, P.: The dependence of the springtime recovery of CO2 uptake in Scots pine on temperature and internal factors, Flora, 169, 398–404, 1980. Rannik, Ü., Kolari, P., Vesala, T., and Hari, P.: Uncertainties in measurement and modelling of net ecosystem exchange of a forest, Agr. Forest Meteorol., 138, 244–257, 2006. Rayment, M. B., Loustau, D., and Jarvis, P. G.: Photosynthesis and respiration of black spruce at three organizational scales: shoot, branch and canopy, Tree Physiol., 22, 219–229, 2002. 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, A., Berbigier, P., Bernhofer, C., Buchmann, N., Gilmanov, T., 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., Yakir, D., and Valentini, R.: On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm, Global Change Biol., 11, 1424–1439, 2005. Repo, T., Hänninen, H., and Kellomäki, S.: The effects of long-term elevation of air temperature and CO2 on the frost hardiness of Scots pine, Plant Cell Environ., 19, 209–216, 1996. Repo, T., Leinonen, I., Wang, K.-Y., and Hänninen, H.: Relation between photosynthetic capacity and cold hardiness in Scots pine, Physiol. Plantarum, 126, 224–231, 2006. Ricciuto, D. M., Butler, M. P., Davis, K. J., Cook, B. D., Bakwin, P. S., Andrews, A., and Teclaw, R. M.: Causes of interannual variability in ecosystem-atmosphere CO2 exchange in a northern Wisconsin forest using a Bayesian model calibration, Agr. Forest Meteorol., 148, 309–327, 2008. Roberntz, P. and Stockfors, J.: Effects of elevated CO2 concentration and nutrition on net photosynthesis, stomatal conductance and needle respiration of field-grown Norway spruce trees, Tree Physiol., 18, 233–241, 1998. Sasai, T., Okamoto, K., Hiyama, T., and Yamaguchi, Y.: Comparing terrestrial carbon fluxes from the scale of a flux tower to the global scale, Ecol. Model., 208, 135–144, 2007. Schulze, E.-D.: Biological control of the terrestrial carbon sink, Biogeosciences, 3, 147–166, online available at: http://www.biogeosciences.net/3/147/2006/, 2006. Sellers, P. J.: Canopy reflectance, photosynthesis and transpiration, Int. J. Remote Sens., 6, 1335–1372, 1985. Sellers, P. J., Berry, J. A., Collatz, G. J., Field, C. B., and Hall, F. G.: Canopy reflectance, photosynthesis, and transpiration. III. A reanalysis using improved leaf models and a new canopy integration scheme, Remote Sens. Environ., 42, 187–216, 1992. Sellers, P. J., Los, S. O., Tucker, C. J., Justice, C. O., Dazlich, D. A. Collatz, G. J., and Randall, D. A.: A revised land surface parameterization (SiB2) for atmospheric GCMs. Part II: The generation of global fields of terrestrial biophysical parameters from satellite data, J. Clim., 9, 706–737, 1996. Solantie, R.: Daytime temperature sum – a new thermal variable describing growing season characteristics and explaining evapotranspiration, Boreal Env. Res., 9, 319–333, 2004. Solantie, R.: Productivity of boreal forests in relation to climate and vegetation zones, Boreal Env. Res., 10, 275–297, 2005. Steinbrecher, R., Hauff, K., Hakola, H., and Rössler, J.: A revised parameterization for emission modeling of isoprenoids for boreal plants, in: Biogenic VOC emissions and photochemistry in the boreal regions of Europe – Biphorep., Final report, Edited by: Laurila, T. and Lindfors, V., European Commission, 158 pp., 1999. Stenberg, P., De Lucia, E. H., Schoettle, A. W. and Smolander, H.: Photosynthetic light capture and processing from cell to canopy, in: Resource physiology of conifers, edited by: Smith, W., Hinckley T., and Roy, J.). Academic Press, Ltd., London, 3–38, 1995. Stockfors, J. and Linder, S.: The effect of nutrition on the seasonal course of needle respiration in Norway spruce stands, Trees, 12, 130–138, 1998. Tanja, S., Berninger, F., Vesala, T., Markkanen, T., Hari, P., Mäkelä, A., Ilvesniemi, H. Hänninen, H., Nikinmaa, E., Huttula, T., Laurila, T., Aurela, M., Grelle, A., Lindroth, A., Arneth, A., Shibistova, O., and Lloyd, J.: Air temperature triggers the recovery of evergreen boreal forest photosynthesis in spring, Global Change Biol., 9, 1410–1426, 2003. Thornley, J. H. M.: Instantaneous canopy photosynthesis: Analytical expressions for sun and shade leaves based on exponential light decay down the canopy and an acclimated non-rectangular hyperbola for leaf photosynthesis, Ann. Bot.-London, 89, 451–458, 2002. Thum, T., Aalto T., Laurila, T., Aurela, M., Kolari, P., and Hari, P: Parametrization of two photosynthesis models at the canopy scale in a northern boreal Scots pine forest, Tellus, 59B, 874–890, 2007. Trenberth, K. E., Jones, P. D., Ambenje, P., Bojariu, R., Easterling, D., Klein Tank, A., Parker, D., Rahimzadeh, F., Renwick, J. A., Rusticucci, M., Soden, B., and Zhai, P.: Observations: Atmospheric surface and climate change, in: Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tiggnor, M., and Miller, H. L., Cambridge University Press, UK and New York, NY, USA, 235–336, 2007. Tuzet, A., Perrier, A., and Leuning, R.: A coupled model of stomatal conductance, photosynthesis and transpiration, Plant Cell Environ., 26, 1097–1116, 2003. Verbeeck, H., Samson, R., Verdonck, F., and Lemeur, R.: Parameter sensitivity and uncertainty of the forest carbon flux model FORUG: a Monte Carlo analysis, Tree Phys., 26, 807–817, 2006. Verbeeck, H., Samson, R., Granier, A., Montpied, P., and Lemeur, R.: Multi-year model analysis of GPP in a temperate beech forest in France, Ecol. Model., 210, 85–103, 2008. Vesala, T., Haataja, J., Aalto, P., Altimir, N., Buzorius, G., Garam, E., Hämeri, K., Ilvesniemi, H., Jokinen, V., Keronen, P., Lahti, T., Markkanen, T., Mäkelä, J. M., Nikinmaa, E., Palmroth, S., Palva, L., Pohja, T., Pumpanen, J., Rannik, Ü., Siivola, E., Ylitalo, H., Hari, P., and Kulmala, M..: Long-term field measurements of atmosphere-surface interactions in boreal forest combining forest ecology, micrometeorology, aerosol physics and atmospheric chemistry, Trends in Heat, Mass and Momentum Transfer, 4, 17–35, 1998. Vesala, T., Suni, T., Rannik, Ü., Keronen, P., Markkanen, T., Sevanto, S., Grönholm, T., Smolander, S., Kulmala, M., Ilvesniemi, H., Ojansuu, R., Uotila, A., Levula, J., Mäkelä, A., Pumpanen, J., Kolari, P., Kulmala, L., Altimir, N., Berninger, F., Nikinmaa, E., and Hari, P.: Effect of thinning on surface fluxes in a boreal forest, Global Biogeochem. Cy., 19, GB2001, doi:10.1029/2004GB002316, 2005. Wang, K. Y., Kellomäki, S., and Laitinen, K.: Acclimation of photosynthetic parameters in Scots pine after three-year exposure to elevated CO2 and temperature, Agr. Forest Meteorol., 82, 195–217, 1996. Wang, Y. P., Baldocchi, D., Leuning, R., Falge, E., and Vesala, T.: Estimating parameters in a land-surface model by applying nonlinear inversion to eddy covariance flux measurements from eight FLUXNET sites, Global Change Biol., 12, 1–19, 2006. Way, D. A. and Sage, R. F.: Elevated growth temperatures reduce the carbon gain of black spruce [\textitPicea mariana (Mill.) B. S. P.], Global Change Biol., 14, 623–636, 2008. Wilson, K. B., Baldocchi, 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. Wu, Y., Brashers, B., Finkelstein, P. L., and Pleim, J. E.: A multilayer biochemical dry deposition model, 1. Model formulation. J. Geophys. Res., 108, 4013–4025, 2003. Wullschleger, S. D.: Biochemical limitations to carbon assimilation in C3 plants – A retrospective analysis of the A/C$_i$ curve from 109 species, J. Exp. Bot, 44, 907–920, 1993. Xu, L. and Baldocchi, D.: Seasonal trends in photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature, Tree Phys., 23, 865–877, 2003.