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1. Low sensitivity of gross primary production to elevated CO2 in a mature eucalypt woodland

Author

Yang, J., Medlyn, B.E., De, Kauwe, M.G., Duursma, R.A., Jiang, M., Kumarathunge, D., Crous, K.Y., Gimeno, T.E., Wujeska-Klause, A., and Ellsworth, D.S.

Abstract

The response of mature forest ecosystems to a rising atmospheric carbon dioxide concentration (span classCombining double low line"inline-formula"iC/ia/span) is a major uncertainty in projecting the future trajectory of the Earth's climate. Although leaf-level net photosynthesis is typically stimulated by exposure to elevated span classCombining double low line"inline-formula"iC/ia/span (espan classCombining double low line"inline-formula"iC/ia/span), it is unclear how this stimulation translates into carbon cycle responses at the ecosystem scale. Here we estimate a key component of the carbon cycle, the gross primary productivity (GPP), of a mature native eucalypt forest exposed to free-air span classCombining double low line"inline-formula"CO2/span enrichment (the EucFACE experiment). In this experiment, light-saturated leaf photosynthesis increased by 19andthinsp;% in response to a 38andthinsp;% increase in span classCombining double low line"inline-formula"iC/ia/span. We used the process-based forest canopy model, MAESPA, to upscale these leaf-level measurements of photosynthesis with canopy structure to estimate the GPP and its response to espan classCombining double low line"inline-formula"iC/ia/span. We assessed the direct impact of espan classCombining double low line"inline-formula"iC/ia/span, as well as the indirect effect of photosynthetic acclimation to espan classCombining double low line"inline-formula"iC/ia/span and variability among treatment plots using different model scenarios./p At the canopy scale, MAESPA estimated a GPP of 1574andthinsp;gandthinsp;Candthinsp;mspan classCombining double low line"inline-formula"-2/spanandthinsp;yrspan classCombining double low line"inline-formula"-1/span under ambient conditions across 4 years and a direct increase in the GPP of span classCombining double low line"inline-formula"+/span11andthinsp;% in response to espan classCombining double low line"inline-formula"iC/ia/span. The smaller canopy-scale response simulated by the model, as compared with the leaf-level response, could be attributed to the prevalence of RuBP regeneration limitation of leaf photosynthesis within the canopy. Photosynthetic acclimation reduced this estimated response to 10andthinsp;%. After taking the baseline variability in the leaf area index across plots in account, we estimated a field GPP response to espan classCombining double low line"inline-formula"iC/ia/span of 6andthinsp;% with a 95andthinsp;% confidence interval (span classCombining double low line"inline-formula"-/span2andthinsp;%, 14andthinsp;%). These findings highlight that the GPP response of mature forests to espan classCombining double low line"inline-formula"iC/ia/span is likely to be considerably lower than the response of light-saturated leaf photosynthesis. Our results provide an important context for interpreting the espan classCombining double low line"inline-formula"iC/ia/span responses of other components of the ecosystem carbon cycle. © Author(s) 2020. Martin G. De Kauwe was supported by the NSW Research Attraction and Acceleration Program (RAAP). Euc-FACE was built as an initiative of the Australian Government as part of the Nation Building Economic Stimulus Plan and is supported by the Australian Commonwealth in collaboration with Western Sydney University.

Published
2020

2. Global variability in leaf respiration in relation to climate, plant functional types and leaf traits

Author

Shuang Xiang, Trofim C. Maximov, Lucy Rowland, Stephen Sitch, Keith J. Bloomfield, Emanuel Gloor, Christopher H. Lusk, Danielle Creek, Nicholas Mirotchnick, Ülo Niinemets, Michael G. Ryan, Peter B. Reich, Jon Lloyd, Fernando Valladares, Joana Zaragoza-Castells, Mary A. Heskel, John J. G. Egerton, Matthew H. Turnbull, Erik J. Veneklaas, John R. Evans, Roberta E. Martin, Jens Kattge, Françoise Yoko Ishida, Kevin L. Griffin, Gerhard Bönisch, Norma Salinas, Michael J. Liddell, Desmond Ng, Jeffrey S. Dukes, Martijn Slot, Hans Lambers, Lina M. Mercado, Pieter Poot, Mark C. Vanderwel, Kirk R. Wythers, Ian J. Wright, Nicholas G. Smith, Lasantha K. Weerasinghe, Rossella Guerrieri, Chris Huntingford, Jen Xiang, Teresa E. Gimeno, Yadvinder Malhi, Paul P. G. Gauthier, Patrick Meir, Eric G. Cosio, Odhran S. O'Sullivan, Gregory P. Asner, Mark G. Tjoelker, Damien Bonal, Lucas A. Cernusak, Graham D. Farquhar, Christian Wirth, Lourens Poorter, Matt Bradford, I. Colin Prentice, Oliver L. Phillips, Tomas F. Domingues, Belinda E. Medlyn, Nikolaos M. Fyllas, Owen K. Atkin, Kristine Y. Crous, Ayal P. Maksimov, Atkin O.K., Bloomfield K.J., Reich P.B., Tjoelker M.G., Asner G.P., Bonal D., Bonisch G., Bradford M.G., Cernusak L.A., Cosio E.G., Creek D., Crous K.Y., Domingues T.F., Dukes J.S., Egerton J.J.G., Evans J.R., Farquhar G.D., Fyllas N.M., Gauthier P.P.G., Gloor E., Gimeno T.E., Griffin K.L., Guerrieri R., Heskel M.A., Huntingford C., Ishida F.Y., Kattge J., Lambers H., Liddell M.J., Lloyd J., Lusk C.H., Martin R.E., Maksimov A.P., Maximov T.C., Malhi Y., Medlyn B.E., Meir P., Mercado L.M., Mirotchnick N., Ng D., Niinemets U., O'Sullivan O.S., Phillips O.L., Poorter L., Poot P., Prentice I.C., Salinas N., Rowland L.M., Ryan M.G., Sitch S., Slot M., Smith N.G., Turnbull M.H., Vanderwel M.C., Valladares F., Veneklaas E.J., Weerasinghe L.K., Wirth C., Wright I.J., Wythers K.R., Xiang J., Xiang S., Zaragoza-Castells J., Australian National University (ANU), Hawkesbury Institute for the Environment [Richmond] (HIE), Western Sydney University, University of Minnesota [Twin Cities] (UMN), University of Minnesota System, Carnegie Institution for Science [Washington], Ecologie et Ecophysiologie Forestières [devient SILVA en 2018] (EEF), Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), Max-Planck-Institut für Biogeochemie (MPI-BGC), CSIRO Land and Water, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), James Cook University (JCU), Pontificia Universidad Católica del Perú (PUCP), Universidade de São Paulo (USP), Purdue University [West Lafayette], National and Kapodistrian University of Athens (NKUA), Department of Geosciences [Princeton], Princeton University, School of Geography [Leeds], University of Leeds, Lamont-Doherty Earth Observatory (LDEO), Columbia University [New York], School of Geosciences [Edinburgh], University of Edinburgh, University of New Hampshire (UNH), Centre for Ecology and Hydrology [Wallingford] (CEH), Natural Environment Research Council (NERC), School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, The University of Western Australia (UWA), Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, UK, University of Waikato [Hamilton], Institute of Biological Problems of the Cryolithozone, Russian Academy of Sciences [Moscow] (RAS), School of Geography and the Environment [Oxford] (SoGE), University of Oxford [Oxford], Macquarie University, College of Life and Environmental Sciences, University of Exeter, Department of Ecology and Evolutionary Biology [University of Toronto] (EEB), University of Toronto, Wageningen University and Research [Wageningen] (WUR), School of Biological Sciences, University of Canterbury, Colorado State University [Fort Collins] (CSU), Department of Biology [Gainesville] (UF|Biology), University of Florida [Gainesville] (UF), Smithsonian Tropical Research Institute, University of Regina (UR), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), University of Peradeniya, Universität Leipzig [Leipzig], Chinese Academy of Sciences [Beijing] (CAS), Western Sydney University (UWS), University of Minnesota [Twin Cities], National and Kapodistrian University of Athens = University of Athens (NKUA | UoA), School of Geography and the Environment [Oxford], Estonian University of Life Sciences, Wageningen University and Research Centre [Wageningen] (WUR), Department of Biology (University of Florida), University of Florida [Gainesville], Smithsonian Tropical Research Institute, Panama City, Republic of Panama., Consejo Superior de Investigaciones Científicas [Spain] (CSIC), and AXA Research Fund

Subjects
temperature sensitivity, Physiology, [SDV]Life Sciences [q-bio], Acclimatization, Climate, Plant Science, Photosynthesis, Aridity, Temperatures, Ecology, Respiration, Temperature, Biosphere, Plants, PE&RC, Phenotype, nitrogen concentration, Leaf nitrogen (N), Plant Leave, Life Sciences & Biomedicine, Woody plant, terrestrial carbon-cycle, thermal-acclimation, Nitrogen, Plant Biology & Botany, Cell Respiration, Climate change, Biology, FOTOSSÍNTESE, Climate model, Ecology and Environment, tropical rain-forests, Carbon cycle, Climate models, Carbon Cycle, Photosynthesi, 07 Agricultural and Veterinary Sciences, Bosecologie en Bosbeheer, Plant functional types (PFTs), elevated atmospheric co2, photosynthetic capacity, Science & Technology, Plant Sciences, Tropics, scaling relationships, Plant, 15. Life on land, Herbaceous plant, 06 Biological Sciences, Carbon Dioxide, Models, Theoretical, vegetation models, Photosynthetic capacity, Arid, Forest Ecology and Forest Management, Plant Leaves, Biology and Microbiology, 13. Climate action, dark respiration, Acclimation
Abstract

Owen K. Atkin [et al.].- Received: 8 July 2014, Accepted: 29 November 2014, Leaf dark respiration (Rdark) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits., Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed-effects models were used to disentangle sources of variation in Rdark., Area-based Rdark at the prevailing average daily growth temperature (T) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8–28°C). By contrast, Rdark at a standard T (25°C, Rdark25) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher Rdark25 at a given photosynthetic capacity (Vcmax25) or leaf nitrogen concentration ([N]) than species at warmer sites. Rdark25 values at any given Vcmax25 or [N] were higher in herbs than in woody plants., The results highlight variation in Rdark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of Rdark in terrestrial biosphere models (TBMs) and associated land-surface components of Earth system models (ESMs).

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