Challenges for evaluating process-based models of gas exchange

R. Grote, J. Korhonen, I. Mammarella


Physiologically-based (or process-based) models are commonly applied to describe plant responses mechanistically in dependence on environmental conditions. They are increasingly evaluated with eddy-covariance measurements that integrate carbon and water exchange of an area of several hectares (called the fetch). However, almost all models applied to date in such exercises have considered only the dominant tree species and neglected other species that contributed to the measured gas exchange rates-either in separate patches or in mixture. This decreases the transferability of the model from one site to another because the contributions from other species might be different. It is therefore a major challenge in modeling today to separate the measured gas exchanges by sources. In this study, a detailed physiologically-based biosphere model is applied that allows distinguishing between tree species in mixed forests, considering them as «vegetation cohorts» that interact with each other. The sensitivity of the model to different assumptions about how different tree species contribute to an integrated measurement of standscale gas exchange is investigated. The model exercise is carried out for a forest site in Finland with dominant Scots pine but presence of significant amounts of Norway spruce and birch. The results demonstrate that forest structure affects simulated gas exchange rates indicating a possible importance of considering differences in physiological properties at the species level. It is argued that the variation of stand structure within the range of eddy-covariance measurements should be better accounted for in models and that inventory measurements need to consider this variation.


forest structure; understorey; physiologically-oriented model; eddy-flux measurements; sensitivity

Full Text:



Aalto T., Juurola E., 2001. Parametrization of a biochemical CO2 exchange model for birch (Betula pendula Roth.). Boreal Env Res 6, 53-64.

Aalto T., Hari P., Vesala T., 2002. Comparison of an optimal stomatal regulation model and a biochemical model in explaining CO2 exchange in field conditions. Silva Fennica 36, 615-623.

Alriksson A., Eriksson H.M., 1998. Variations in mineral nutrient and C distribution in the soil and vegetation compartments of five temperate tree species in NE Sweden. For Ecol Manage 108, 261-273.

Aubinet M., Grelle A., Ibrom A., Rannik Ü., Moncrieff J., Foken T., Kowalski A.S., Martin P.H., Bernhofer C., Clement R., Elbers J., Granier A., Grünwald T., Morgenstern K., Pilegaard K., Rebmann C., Snijders W., Valentini R., Vesala T., 2000. Estimates of the annual net carbon and water exchange of forests: the EUROFLUX methodology. Adv Ecol Res 30, 113-175.

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., Mahli Y., Meyers T., Munger W., Oechel W., Paw-U K.T., Pilegaard K., Schmid H.P., Valentini R., Verma S., Vesala T., Wilson K., Wofsy S., 2001. Fluxnet: a new tool to study the temporal and spatial variability of ecosystemscale carbon dioxide, water vapor, and energy flux densities. B Am Meteorol Soc 82, 2415-2434.<2415:FANTTS>2.3.CO;2

Ball J.T., Woodrow I.E., Berry J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: Progress in photosynthesis research (Biggins J., ed). Martinus-Nijhoff Publishers, Dordrecht, The Netherlands. pp. 221-224. PMid:2822254

Battaglia M., Sands P., White D., Mummery D., 2004. CABALA: a linked carbon, water and nitrogen model of forest growth for silvicultural decision support. For Ecol Manage 193, 251-282.

Bergh J., Mcmurtrie R.E., Linder S., 1998. Climatic factors controlling the productivity of Norway spruce: a model-based analysis. For Ecol Manage 110, 127-139.

Bergh J., Freeman M., Sigurdsson B.D., Kellomäki S., Laitinen K., Niinistö S., Peltola H., Linder S., 2003. Modelling the short-term effects of climate change on the productivity of selected tree species in Nordic countries. For Ecol Manage 183, 327-340.

Berninger F., 1994. Simulated irradiance and temperature estimates as a possible source of bias in the simulation of photosynthesis. Agric Forest Meteorol 71, 19-32.

Bossel H., 1996. TREEDYN3 forest simulation model. Ecol Modell 90, 187-227.

Butterbach-Bahl K., Kahl M., Mykhayliv L., Werner C., Kiese R., Li C., 2009. A European-wide inventory of soil NO emissions using the biogeochemical models DNDC/Forest-DNDC. Atmos Environ 43, 1392-1402.

Constable J.V.H., FRIEND A.L., 2000. Suitability of process-based tree-growth models for addressing tree response to climate change. Environ Pollut 110, 47-59.

Coops N.C., Waring R.H., 2001. Assessing forest growth across southwestern Oregon under a range of current and future global change scenarios using a process model, 3-PG. Global Change Biol 7, 15-29.

De Wit C.T., Goudriaan J., Van Laar H.H., Penning De Vries F.W.T., Rabbinge R., Van Keulen H., 1978. Simulation of assimilation, respiration and transpi ration of crops. Centre for Agricultural Publishing and Documentation (Pudoc), Wageningen, The Netherlands. PMCid:525907

Deckmyn G., Op De Beeck M., Löw M., Then C., Verbeeck H., Wipfler P., Ceulemans R., 2007. Modelling ozone effects on adult beech trees through simulation of defence, damage, and repair costs: implementation of the CASIROZ ozone model in the ANAFORE forest model. Plant biol (Stutt) 9, 320-330.

Deckmyn G., Campioli M., Muys B., Kraigher H., 2011. Simulating C cycles in forest soils: including the active role of micro-organisms in the ANAFORE forest model. Ecol Modell 222, 1972-1985.

Deckmyn G., Mali B., Kraigher H., Trorelli N., Op De Beeck M., Ceulemans R., 2009. Using the process-based stand model ANAFORE including Bayesian optimisation to predict wood quality and quantity and their uncertainty in Slovenian beech. Silva Fennica 43, 523-534.

Delagrange S., 2011. Light- and seasonal-induced plasticity in leaf morphology, N partitioning and photosynthetic capacity of two temperate deciduous species. Environ Exp Bot 70, 1-10.

Ditzer T., Glauner R., Förster M., Köhler P., Huth A., 2000. The process-based stand growth Formix 3-Q applied in a GIS environment for growth and yield analysis in a tropical rain forest. Tree Physiol 20, 367-381. PMid:12651452

Duursma R.A., Kolari P., Peramaki M., Pulkkinen M., Mäkelä A., Nikinmaa E., Hari P., Aurela M., Berbigier P., Bernhofer Ch., Grünwald T., Loustau D., Molder M., Verbeeck H., Vesala T., 2009. Contributions of climate, leaf area index and leaf physiology to variation in gross primary production of six coniferous forests across Europe: a model-based analysis. Tree Physiol 29, 621-639. PMid:19324698

Falge E., Graber W., Siegwolf R., Tenhunen J.D., 1996. A model of the gas exchange response of Picea abies to habitat conditions. Trees 10, 277-287.

Falge E., Ryel R.J., Alsheimer M., Tenhunen J.D., 1997. Effects of stand structure and physiology on forest gas exchange: a simulation study for Norway spruce. Trees 11, 436-448.

Farquhar G.D., Von Caemmerer S., Berry J.A., 1980. A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species. Planta 149, 78-90.

Flechard C.R., Nemitz E., Smith R.G., Fowler D., Vermeulen A.T., Bleeker A., Erisman J.W., Simpson D., Zhang L., Tang Y.S., Sutton M.A., 2011. Dry deposition of reactive nitrogen to European ecosystems: a comparison of inferential models across the NitroEurope network. Atmos Chem Phys 11, 2703-2728.

Groenendijk M., Dolman A.J., Van Der Molen M.K., Leuning R., Arneth A., Delpierre N., Gash J.H.C., Lindroth A., Richardson A.D., Verbeeck H., Wohlfahrt G., 2011. Assessing parameter variability in a photosynthesis model within and between plant functional types using global Fluxnet eddy covariance data. Agric Forest Meteorol 151, 22-38.

Grote R., 1998. Integrating dynamic morphological properties into forest growth modeling. II. Allocation and mortality. For Ecol Manage 111, 193-210.

Grote R., 2003. Estimation of crown radii and crown projection area from stem size and tree position. Ann For Sci 60, 393-402.

Grote R., Lavoir A.V., Rambal S., Staudt M., Zimmer I., Schnitzler J.-P., 2009. Modelling the drought impact on monoterpene fluxes from an evergreen Mediterranean forest canopy. Oecologia 160, 213-223. PMid:19219456

Grote R., 2007. Sensitivity of volatile monoterpene emission to changes in canopy structure – A model based exercise with a process-based emission model. New Phytol 173, 550-561. PMid:17244049

Grote R., Lehmann E., Brümmer C., Brüggemann N., Szarzynski J., Kunstmann H., 2009. Modelling and observation of biosphere-atmosphere interactions in natural savannah in Burkina Faso, West Africa. Phys Chem Earth 34, 251-260.

Grote R., Kiese R., Grünwald T., Ourcival J.-M., Granier A., 2011. Modelling forest carbon balances considering tree mortality and removal. Agric Forest Meteorol 151, 179-190.

Hari P., Hänninen H., Berninger F., Kolari P., Nikinmaa E., Mäkelä A., 2009. Predicting boreal conifer photosynthesis in field conditions. Boreal Environment Research 14, 19-28.

Hari P., Kulmala M., 2005. Station for measuring ecosystem-atmosphere relations (SMEAR II). Boreal Env Res 10, 315-322.

Havranek W.M., Benecke U., 1978. The influence of soil moisture on water potential, transpiration and photosynthesis of conifer seedlings. Plant Soil 49, 91-103.

Holst J., Grote R., Offermann C., Ferrio J.P., Gessler A., Mayer H., Rennenberg H., 2010. Water fluxes within beech stands in complex terrain. Int J Biometeorol 54, 23-36. PMid:19629535

Ilvesniemi H., Levula J., Ojansuu R., Kolari P., Kulmala L., Pumpanen J., Launiainen S., Vesala T., Nikinmaa E., 2009. Long-term measurements of the carbon balance of a boreal Scots pine dominated forest ecosystem. Boreal Env Res 14, 731-753.

Ilvesniemi H., Pumpanen J., Duursma R., Hari P., Keronen P., Kolari P., Kulmala M., Mammarella I., Nikinmaa E., Rannik Ü., Pohja T., Siivola E., Vesala T., 2010. Water balance of a boreal Scots pine forest. Boreal Env Res 15, 375-396.

Jach M.E., Ceulemans R., 1999. Effects of elevated atmospheric CO2 on phenology, growth and crown structure of Scots pine (Pinus sylvestris) seedlings after two years of exposure in the field. Tree Physiol 19, 289-300. PMid:12651572

Jacobsen C., Rademacher P., Meesenburg H., Meiwes K.J., 2003. Gehalte chemischer Elemente in Baumkompartimenten - Literaturstudie und Datensammlung. Berichte des Forschungszentrum Waldökosysteme. pp. 1-80.

Jarvis P.G., 1976. The interpretation of leaf water potential and stomatal conductance found in canopies in the field. Phil Trans R Soc Lond B 273, 593-610.

Kellomäki S., Wang K.-Y., 1997. Effects of elevated O3 and CO2 concentrations on photosynthesis and stomatal conductance in Scots pine. Plant Cell Environ 20, 995-1006.

Kesik M., Brüggemann N., Forkel R., Kiese R., Knoche R., Li C., Seufert G., Simpson D., Butterbach-Bahl K., 2006. Future scenarios of N2O and NO emissions from European forest soils. J Geophys Res 111. doi: 10.1029/2005JG000115pp.

Keskitalo E.C.H., 2011. How can forest management adapt to climate change? Possibilities in different forestry systems. Forests 2, 415-430.

Kimball J.S., Keyser A.R., Running S.W., Saatchi S.S., 2000. Regional assessment of boreal forest productivity using an ecological process model and remote sensing parameter maps. Tree Physiol 20, 761-775. PMid:12651512

Kolari P., Pumpanen J., Rannik Ü., Ilvesniemi H., Hari P., Berninger F., 2004. Carbon balance of different aged Scots pine forests in Southern Finland. Global Change Biol 10, 1106-1119.

Kolari P., Pumpanen J., Kulmala L., Ilvesniemi H., Nikinmaa E., Grönholm T., Hari P., 2006. Forest floor vegetation plays an important role in photosynthetic production of boreal forests. For Ecol Manage 221, 241-248.

Korhonen J.F.J., Pumpanen J., Kolari P., Juurola E., Nikinmaa E., 2009. Contribution of root and rhizosphere respiration to the annual variation of carbon balance of a boreal Scots pine forest. Biogeosciences Discuss 6, 6179-6204.

Kram P., Santore R.C., Driscoll C.T., Aber J.D., Hruska J., 1999. Application of the forest-soil-water model (PnET-BGC/CHESS) to the Lysina catchment, Czech Republic. Ecol Modell 120, 9-30.

Kramer K., Leinonen I., Bartelink H.H., Berbigier P., Borghetti M., Bernhofer Ch., Cienciala E., Dolman A.J., Froer O., Gracia C.A., Granier A., Grünwald T., Hari P., Jans W., Kellomäki S., Loustau D., Magnani F., Markkanen T., Matteucci G., Mohren G.M.J., Moors E., Nissinen A., Peltola H., Sabaté S., Sanchez A., Sontag M., Valentini R., Vesala T., 2002. Evaluation of six process-based forest growth models using eddy-covariance measurements of CO2 and H2O fluxes at six forest sites in Europe. Global Change Biol 8, 213-230.

Kuuluvainen T., 1991. Long-term development of needle mass, radiation interception and stemwood production in naturally regenerated Pinus sylvestris stands on Empetrum-Vaccinium site type in the northern boreal zone in Finland: an analysis based on an empirical study and simulation. For Ecol Manage 46, 103-122.

Landsberg J., Johnsen K., Albaugh T., Allen H., Mckeand S., 2001. Applying 3-PG, a simple processbased model designed to produce practical results to data from loblolly pine experiments. Forest Sci 47, 43-51.

Landsberg J., 2003. Physiology in forest models: history and the future. FBMIS 1, 49-63.

Lasch P., Badeck F.-W., Suckow F., Lindner M., Mohr P., 2005. Model-based analysis of management alternatives at stand and regional level in Brandenburg (Germany). For Ecol Manage 207, 59-74.

Lehning A., Zimmer W., Zimmer I., Schnitzler J.-P., 2001. Modeling of annual variations of oak (Quercus robur L.) isoprene synthase activity to predict isoprene emission rates. J Geophys Res 106, 3157-3166.

Li C., Aber J., Stange F., Butterbach-Bahl K., Papen H., 2000. A process-oriented model of N2O and NO emissions from forest soils 1. Model development. J Geophys Res 105, 4369-4384.

Li C., Frolking S., Frolking T.A., 1992. A model of nitrous oxide evolution from soil driven by rainfall events: 1. Model structure and Sensitivity. J Geophys Res 97, 9759-9776.

Linkosalo T., Häkkinen R., Hänninen H., 2006. Models of the spring phenology of boreal and temperate trees: is there something missing? Tree Physiol 26, 1165-1172. PMid:16740492

Long S.P., 1991. Modification of the response of photosynthetic productivity to rising temperature by atmospheric CO2 concentrations: has its importance been underestimated? Plant Cell Environ 14, 729-739.

Mammarella I., Kolari P., Rinne J., Keronen P., Pumpanen J., Vesala T., 2007. Determining the contribution of vertical advection to the net ecosystem exchange at Hyytiälä forest, Finland. Tellus B 59, 900-909.

Mammarella I., Launiainen S., Gronholm T., Keronen P., Pumpanen J., Rannik Ü., Vesala T., 2009. Relative humidity effect on the high-frequency attenuation of water vapor flux measured by a closed-path eddy covariance system. J Atmos Oceanic Technol 26, 1856-1866.

Markkanen T., Rannik Ü., Marcolla B., Cescatti A., Vesala T., 2003. Footprints and fetches for fluxes over forest canopies with varying structure and density. Bound Layer Meteorol 106, 437-459.

Maurer S., Matyssek R., 1997. Nutrition and the ozone sensitivity of birch (Betula pendula) - II. Carbon balance, water-use efficiency and nutritional status of the whole plant. Trees 12, 11-20.

Mäkelä A., Landsberg J., Ek A.R., Burk T.E., Termikaelian M., Ågren G.I., Oliver C.D., Puttonen P., 2000. Process-based models for forest ecosystem management: current state of the art and challenges for practical implementation. Tree Physiol 20, 289-298. PMid:12651445

Mäkelä A., Hari P., Berninger F., Hanninen H., Nikinmaa E., 2004. Acclimation of photosynthetic capacity in Scots pine to the annual cycle of temperature. Tree Physiol 24, 369-376. PMid:14757576

Mäkelä A., Kolari P., Karimäki J., Nikinmaa E., Perämäki M., Hari P., 2006. Modelling five years of weather-driven variation of GPP in a boreal forest. Agric Forest Meteorol 139, 382-398.

Mäkelä A., Valentine H.T., Helmisaari H.-S., 2008. Optimal co-allocation of carbon and nitrogen in a forest stand at steady state. New Phytol 180, 114-123. PMid:18637066

Medlyn B.E., Badeck F.-W., De Pury D.G.G., Barton C.V.M., Broadmeadow M., 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., Jstbid P.G., 1999. Effects of elevated (CO2) on photosynthesis in European forest species: a meta-analysis of model parameters. Plant Cell Environ 22, 1475-1495.

Medlyn B.E., Barton C.V.M., Broadmeadow M.S.J., Ceulemans R., Angelis P.D., Forstreuter M., Freeman M., Jackson S.B., Kellomäki S., Laitat E., Rey A., Roberntz P., Sigurdsson B.D., Strassemeyer J., Wang K., Curtis P.S., Jarvis P.G., 2001. Stomatal conductance of forest species after long-term exposure to elevated CO2 concentration: a synthesis. New Phytol 149, 247-264.

Medlyn B.E., Dreyer E., Ellsworth D., Forstreuter M., Harley P.C., Kirschbaum M.U.F., Le Roux X., Montpied P., Strassmeyer J., Walcroft A., Wang K., Loustau D., 2002. Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data. Plant Cell Environ 25, 1167-1179.

Meir P., Kruijt B., Broadmeadow M., Barbosa E., Kull O., Carswell F., Nobre A., Jarvis P.G., 2002. Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit area. Plant Cell Environ 25, 343-357.

Mickler R.A., Earnhardt T.S., Moore J.A., 2002. Modeling and spatially distributing forest net primary production at the regional scale. J Air Waste Manage Assoc 52, 174-185.

Miehle P., Grote R., Battaglia M., Feikema P.M., Arndt S.K., 2010. Evaluation of a process-based ecosystem model for long-term biomass and stand development of Eucalyptus globulus plantations. Eur J Forest Res 129, 377-391.

Monteith J.L., Unsworth M.H., 1990. Principles of Environmental Physics. Edward Arnold, New York.

Moren A.-S., Lindroth A., Flower-Ellis J., Cienciala E., Mölder M., 2000. Branch transpiration of pine and spruce scaled to tree and canopy using needle biomass distributions. Trees 14, 384-397.

Mund M., Kummetz E., Hein M., Bauer G.A., Schulze E.-D., 2002. Growth and carbon stocks of a spruce forest chronosequence in central Europe. For Ecol Manage 171, 275-296.

Perttu K., Bischof W., Grip H., Jansson P.-E., Lindgren A., Lindroth A., Norén B., 1980. Micrometeorology and hydrology of pine forest ecosystems. I. Field studies. In: Structure and function of northern Coniferous forests - An ecosystem Study (Persson T., ed). Stockholm. pp. 75-121.

Pietsch S.A., Hasenauer H., Thornton P.E., 2005. BGC-model parameters for tree species growing in central European forests. For Ecol Manage 211, 264-295.

Portsmuth A., Niinemets Ü., 2007. Structural and physiological plasticity in response to light and nutrients in five temperate deciduous woody species of contrasting shade tolerance. Funct Ecol 21. doi: 10.1111/j.1365-2435.2006.01208.x.

Rannik Ü., Kolari P., Vesala T., 2006. Uncertainties in measurement and modelling of net ecosystem exchange of a forest. Agric Forest Meteorol 138, 244-257.

Richardson A.D., Aikens M., Berlyn G.P., Marshall P., 2004. Drought stress and paper birch (Betula papyrifera) seedlings: effects of an organic biostimulant on plant health and stress tolerance, and detection of stress effects with instrument-based, noninvasive methods. Journal of Arboriculture 30, 52-61.

Richardson A.D., Schenck Bailey A., Denny E.G., Martin C.W., O'keefe J., 2006. Phenology of a northern hardwood forest canopy. Global Change Biol 12, 1174-1188.

Rodrigues A., Pita G., Mateus J., Kurz-Besson C., Casquilho M., Cerasoli S., Gomes A., Pereira J., 2011. Eight years of continuous carbon fluxes measurements in a Portuguese eucalypt stand under two main events: drought and felling. Agric Forest Meteorol 151, 493-507.

Sampson D.A., Janssens I.A., Ceulemans R., 2006. Under-story contributions to stand level GPP using the process model SECRETS. Agric Forest Meteorol 139, 94-104.

Sellers W.K., 1965. Physical climatolgy. University of Chicago Press, Chicago.

Sellin A., Kupper P., 2004. Within-crown variation in leaf conductance of Norway spruce: effects of irradiance, vapour pressure deficit, leaf water status and plant hydraulic constraints. Ann For Sci 61, 419-429.

Sievänen R., 1993. A process-based model for the dimensional growth of even-aged stands. Scand J For Res 8, 28-48.

Silvertown J., 2004. Plant coexistence and the niche. Trends Ecol Evol 19, 605-611.

Suni T., Rinne J., Reissell A., Altimir N., Keronen P., Rannik Ü., Dal Maso M., Kulmala M., Vesala T., 2003. Long-term measurements of surface fluxes above a Scots pine forest in Hyytiälä, southern Finland 1996-2001. Boreal Env Res 8, 287-301.

Thornley J.H.M., Cannell M.G.R., 2000. Modelling the components of plant respiration: representation and realism. Ann Bot 85, 55-67.

Thornley J.H.M., 2002. 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 89, 451-458.

Thum T., Aalto T., Laurila T., Aurela M., Kolari P., Hari P., 2007. Parametrization of two photosynthesis models at the canopy scale in a northern boreal Scots pine forest. Tellus B 59, 874-890.

Tietjen B., Huth A., 2006. Modelling dynamics of managed tropical rainforests – An aggregated approach. Ecol Modell 199, 421-432.

Uddling J., Hall M., Wallin G., Karlsson P.E., 2005. Measuring and modelling stomatal conductance and photosynthesis in mature birch in Sweden. Agric Forest Meteorol 132, 115-131.

Uri V., Vares A., Tullus H., Kanal A., 2007. Aboveground biomass production and nutrient accumulation in young stands of silver birch on abandoned agricultural land. Biomass and Bioenergy 31, 195-204.

Van Gorsel E., Delpierre N., Leuning R., Black A., Munger J.W., Wofsy S., Aubinet M., Feigenwinter C., Beringer J., Bonal D., Chen B., Chen J., Clement R., Davis K.J., Desai A.R., Dragoni D., Etzold S., Grünwald T., Gu L., Heinesch B., Hutyra L.R., Jans W.W.P., Kutsch W., Law B.E., Leclerc M.Y., Mammarella I., Montagnani L., Noormets A., Rebmann C., Wharton S., 2009. Estimating nocturnal ecosystem respiration from the vertical turbulent flux and change in storage of CO2. Agric Forest Meteorol 149, 1919-1930.

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., Hari P., 2005. Effect of thinning on surface fluxes in a boreal forest. Global Biogeochem Cycl 19. doi: 10.1029/2004GB002316pp

Vose J.M., Ryan M.G., 2002. Seasonal respiration of foliage, fine roots, and woody tissues in relation to growth, tissue N, and photosynthesis. Global Change Biol 8, 182-193.

Wang K.-Y., 1996. Canopy CO2 exchange of Scots pine and its seasonal variation after four-year exposure to elevated CO2 and temperature. Agric Forest Meteorol 82, 1-27.

Wang Q., Tenhunen J., Falge E., Bernhofer C., Granier A., Vesala T., 2003. Simulation and scaling of temporal variation in gross primary production for coniferous and deciduous temperate forests. Global Change Biol 10, 37-51.

Zianis D., Muukkonen P., Mäkipää R., Mencuccini M., 2005. Biomass and stem volume equations for tree species in Europe. Silva Fennica Monographs [4], pp. 1-63.

DOI: 10.5424/fs/20112003-11084