Title: Thermal optimality of net ecosystem exchange of carbon dioxide and underlying mechanisms
Abstract: New PhytologistVolume 194, Issue 3 p. 775-783 Full paperFree Access Thermal optimality of net ecosystem exchange of carbon dioxide and underlying mechanisms Shuli Niu, Shuli Niu Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorYiqi Luo, Yiqi Luo Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA Institute of Global Environmental Change Research, Fudan University, Shanghai, ChinaSearch for more papers by this authorShenfeng Fei, Shenfeng Fei Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorWenping Yuan, Wenping Yuan College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, ChinaSearch for more papers by this authorDavid Schimel, David Schimel NEON, Inc., 5340 Airport Blvd, Boulder, CO 80301, USASearch for more papers by this authorBeverly E. Law, Beverly E. Law College of Forestry, Oregon State University, Corvallis, OR 97331-2209, USASearch for more papers by this authorChristof Ammann, Christof Ammann Federal Research Station Agroscope Reckenholz-Tänikon, Reckenholzstr. 191, 8046 Zürich, SwitzerlandSearch for more papers by this authorM. Altaf Arain, M. Altaf Arain School of Geography and Earth Sciences, McMaster University, Hamilton, ON, Canada L8S 4K1Search for more papers by this authorAlmut Arneth, Almut Arneth Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, Sweden Atmospheric Environmental Research, Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, GermanySearch for more papers by this authorMarc Aubinet, Marc Aubinet Faculté Universitaire des Sciences Agronomiques de Gembloux, Unitéde Physique des Biosystémes, B-5030 Gembloux, BelgiumSearch for more papers by this authorAlan Barr, Alan Barr Climate Research Division, Environment Canada, Saskatoon, SK S7N 3H5, CanadaSearch for more papers by this authorJason Beringer, Jason Beringer School of Geography and Environmental Science, Monash University, Clayton, Vic 3800, AustraliaSearch for more papers by this authorChristian Bernhofer, Christian Bernhofer Institute of Hydrology and Meteorology, Chair of Meteorology, Technische Universität Dresden, 01062 Dresden, GermanySearch for more papers by this authorT. Andrew Black, T. Andrew Black Land and Food Systems, University of British Columbia, Vancouver, BC, Canada V6T 1Z4Search for more papers by this authorNina Buchmann, Nina Buchmann ETH, Zurich, Institute of Plant Science, Universitaetsstrasse 2, Zürich 8092, SwitzerlandSearch for more papers by this authorAlessandro Cescatti, Alessandro Cescatti European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, ItalySearch for more papers by this authorJiquan Chen, Jiquan Chen Department of Environmental Sciences (DES), University of Toledo, Toledo, OH 43606, USASearch for more papers by this authorKenneth J. Davis, Kenneth J. Davis Earth System Science Center, Pennsylvania State University, State College, PA 16802, USASearch for more papers by this authorEbba Dellwik, Ebba Dellwik Wind Energy Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. 49, DK-4000 Roskilde, DenmarkSearch for more papers by this authorAnkur R. Desai, Ankur R. Desai Department of Atmospheric and Oceanic Sciences, University of Wisconsin, Madison, WC, 53706, USASearch for more papers by this authorSophia Etzold, Sophia Etzold ETH, Zurich, Institute of Plant Science, Universitaetsstrasse 2, Zürich 8092, SwitzerlandSearch for more papers by this authorLouis Francois, Louis Francois Unité de Modélisation du Climat et des Cycles Biogéochimiques (UMCCB) Université de Liège, B-4000 Liège, BelgiumSearch for more papers by this authorDamiano Gianelle, Damiano Gianelle Sustainable Agro-ecosystems and Bioresources Department, IASMA Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 San Michele all’Adige, (TN), ItalySearch for more papers by this authorBert Gielen, Bert Gielen Department of Biology, University of Antwerpen, Universiteitsplein 1, Wilrijk, B-2610, BelgiumSearch for more papers by this authorAllen Goldstein, Allen Goldstein Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94720, USASearch for more papers by this authorMargriet Groenendijk, Margriet Groenendijk Department of Earth Science, Faculty of Earth and Life Sciences, VU University Amsterdam, Boelelaan 1085, 1081 HV Amsterdam, the NetherlandsSearch for more papers by this authorLianhong Gu, Lianhong Gu Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USASearch for more papers by this authorNiall Hanan, Niall Hanan Geographic Information Science Center of Excellence (GIScCE), South Dakota State University, 1021 Medary Ave., Wecota Hall 506B, Brookings, SD 57007-3510, USASearch for more papers by this authorCarole Helfter, Carole Helfter Centre for Ecology and Hydrology (CEH), Bush Estate, Penicuik, Midlothian, Scotland EH26 0QB, UKSearch for more papers by this authorTakashi Hirano, Takashi Hirano Hokkaido University N9, W9, Kita-ku, Sapporo, Hokkaido, 060-8589, JapanSearch for more papers by this authorDavid Y. Hollinger, David Y. Hollinger USDA Forest Service, Northern Research Station, Durham, NH 03824, USASearch for more papers by this authorMike B. Jones, Mike B. Jones Botany Department, Trinity College of Dublin, Dublin, IrelandSearch for more papers by this authorGerard Kiely, Gerard Kiely Civil and Environmental Engineering Department, University College Cork, Cork, IrelandSearch for more papers by this authorThomas E. Kolb, Thomas E. Kolb School of Forestry, Northern Arizona University, Flagstaff, AZ 86001, USASearch for more papers by this authorWerner L. Kutsch, Werner L. Kutsch Johann Heinrich von Thünen-Institute (vTI), Institute for Climate Research, Braunschweig, GermanySearch for more papers by this authorPeter Lafleur, Peter Lafleur Department of Geography, Trent University, Peterborough, ON K9J 7B8, CanadaSearch for more papers by this authorDavid M. Lawrence, David M. Lawrence National Center for Atmospheric Research, Boulder, CO 80305, USASearch for more papers by this authorLinghao Li, Linghao Li State Key laboratory of Vegetation and Environmental Changes, Institute of Botany, Chinese Academy of SciencesSearch for more papers by this authorAnders Lindroth, Anders Lindroth Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, SwedenSearch for more papers by this authorMarcy Litvak, Marcy Litvak Biology Department, University of New Mexico, Albuquerque, NM 87131-001, USASearch for more papers by this authorDenis Loustau, Denis Loustau INRA, UR1263 EPHYSE, F-33140, Villenave d’Ornon, FranceSearch for more papers by this authorMagnus Lund, Magnus Lund Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, SwedenSearch for more papers by this authorMichal Marek, Michal Marek Institute of Systems Biology and Ecology, Academy of Sciences of the Czech Republic, Poříčí3b, CZ-60300 Brno, Czech RepublicSearch for more papers by this authorTimothy A. Martin, Timothy A. Martin University of Florida, Gainesville, FL 32611, USASearch for more papers by this authorGiorgio Matteucci, Giorgio Matteucci National Research Council, Institute of Agroenvironmental and Forest Biology, 00015 Monterotondo Scalo (RM), ItalySearch for more papers by this authorMirco Migliavacca, Mirco Migliavacca European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, ItalySearch for more papers by this authorLeonardo Montagnani, Leonardo Montagnani Servizi Forestali, Agenzia per l’Ambiente, Provincia Autonoma di Bolzano, 39100, Bolzano, Italy Faculty of Science and Technology, Free University of Bolzano, Piazza Università 1, 39100 Bolzano, ItalySearch for more papers by this authorEddy Moors, Eddy Moors ESS-CC, Alterra, Wageningen UR, PO Box 47, 6700 AA Wageningen, The Netherlands NLSearch for more papers by this authorJ. William Munger, J. William Munger Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, 02138, USASearch for more papers by this authorAsko Noormets, Asko Noormets North Carolina State University/USDA Forest Service, Southern Global Change Program, Raleigh, NC, 27606, USASearch for more papers by this authorWalter Oechel, Walter Oechel Department of Biology, San Diego State University, San Diego, CA 92182-4614, USASearch for more papers by this authorJanusz Olejnik, Janusz Olejnik Meteorology Department, Poznan University of Life Sciences (PULS), 60-667 Poznan, PolandSearch for more papers by this authorKyaw Tha Paw U, Kyaw Tha Paw U Atmospheric Science Group, LAWR, UC Davis, Davis, CA 95616, USASearch for more papers by this authorKim Pilegaard, Kim Pilegaard Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. 49, DK-4000 Roskilde, DenmarkSearch for more papers by this authorSerge Rambal, Serge Rambal DREAM, CEFE, CNRS, UMR5175, 1919 route de Mende, F-34293 Montpellier, Cedex 5, FranceSearch for more papers by this authorAntonio Raschi, Antonio Raschi CNR – Instituto di Biometeorologia (IBIMET), Via Giovanni Caproni 8, 50145 Firenze, ItalySearch for more papers by this authorRussell L. Scott, Russell L. Scott USDA-ARS Southwest Watershed Research Center, Tucson, AZ 85719, USASearch for more papers by this authorGünther Seufert, Günther Seufert European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, ItalySearch for more papers by this authorDonatella Spano, Donatella Spano Department of Economics and Woody Plant Ecosystems, University of Sassari, Sassari, ItalySearch for more papers by this authorPaul Stoy, Paul Stoy Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, USASearch for more papers by this authorMark A. Sutton, Mark A. Sutton USDA Forest Service, Northern Research Station, Durham, NH 03824, USASearch for more papers by this authorAndrej Varlagin, Andrej Varlagin A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Lenisky pr., 33 Moscow, 119071, RussiaSearch for more papers by this authorTimo Vesala, Timo Vesala Department of Physics, FI-00014, University of Helsinki, FinlandSearch for more papers by this authorEnsheng Weng, Ensheng Weng Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorGeorg Wohlfahrt, Georg Wohlfahrt University of Innsbruck, Institute of Ecology Sternwartestr 15, Innsbruck 6020, AustriaSearch for more papers by this authorBai Yang, Bai Yang Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USASearch for more papers by this authorZhongda Zhang, Zhongda Zhang Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorXuhui Zhou, Xuhui Zhou Institute of Global Environmental Change Research, Fudan University, Shanghai, ChinaSearch for more papers by this author Shuli Niu, Shuli Niu Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorYiqi Luo, Yiqi Luo Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA Institute of Global Environmental Change Research, Fudan University, Shanghai, ChinaSearch for more papers by this authorShenfeng Fei, Shenfeng Fei Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorWenping Yuan, Wenping Yuan College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, ChinaSearch for more papers by this authorDavid Schimel, David Schimel NEON, Inc., 5340 Airport Blvd, Boulder, CO 80301, USASearch for more papers by this authorBeverly E. Law, Beverly E. Law College of Forestry, Oregon State University, Corvallis, OR 97331-2209, USASearch for more papers by this authorChristof Ammann, Christof Ammann Federal Research Station Agroscope Reckenholz-Tänikon, Reckenholzstr. 191, 8046 Zürich, SwitzerlandSearch for more papers by this authorM. Altaf Arain, M. Altaf Arain School of Geography and Earth Sciences, McMaster University, Hamilton, ON, Canada L8S 4K1Search for more papers by this authorAlmut Arneth, Almut Arneth Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, Sweden Atmospheric Environmental Research, Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, GermanySearch for more papers by this authorMarc Aubinet, Marc Aubinet Faculté Universitaire des Sciences Agronomiques de Gembloux, Unitéde Physique des Biosystémes, B-5030 Gembloux, BelgiumSearch for more papers by this authorAlan Barr, Alan Barr Climate Research Division, Environment Canada, Saskatoon, SK S7N 3H5, CanadaSearch for more papers by this authorJason Beringer, Jason Beringer School of Geography and Environmental Science, Monash University, Clayton, Vic 3800, AustraliaSearch for more papers by this authorChristian Bernhofer, Christian Bernhofer Institute of Hydrology and Meteorology, Chair of Meteorology, Technische Universität Dresden, 01062 Dresden, GermanySearch for more papers by this authorT. Andrew Black, T. Andrew Black Land and Food Systems, University of British Columbia, Vancouver, BC, Canada V6T 1Z4Search for more papers by this authorNina Buchmann, Nina Buchmann ETH, Zurich, Institute of Plant Science, Universitaetsstrasse 2, Zürich 8092, SwitzerlandSearch for more papers by this authorAlessandro Cescatti, Alessandro Cescatti European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, ItalySearch for more papers by this authorJiquan Chen, Jiquan Chen Department of Environmental Sciences (DES), University of Toledo, Toledo, OH 43606, USASearch for more papers by this authorKenneth J. Davis, Kenneth J. Davis Earth System Science Center, Pennsylvania State University, State College, PA 16802, USASearch for more papers by this authorEbba Dellwik, Ebba Dellwik Wind Energy Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. 49, DK-4000 Roskilde, DenmarkSearch for more papers by this authorAnkur R. Desai, Ankur R. Desai Department of Atmospheric and Oceanic Sciences, University of Wisconsin, Madison, WC, 53706, USASearch for more papers by this authorSophia Etzold, Sophia Etzold ETH, Zurich, Institute of Plant Science, Universitaetsstrasse 2, Zürich 8092, SwitzerlandSearch for more papers by this authorLouis Francois, Louis Francois Unité de Modélisation du Climat et des Cycles Biogéochimiques (UMCCB) Université de Liège, B-4000 Liège, BelgiumSearch for more papers by this authorDamiano Gianelle, Damiano Gianelle Sustainable Agro-ecosystems and Bioresources Department, IASMA Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 San Michele all’Adige, (TN), ItalySearch for more papers by this authorBert Gielen, Bert Gielen Department of Biology, University of Antwerpen, Universiteitsplein 1, Wilrijk, B-2610, BelgiumSearch for more papers by this authorAllen Goldstein, Allen Goldstein Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94720, USASearch for more papers by this authorMargriet Groenendijk, Margriet Groenendijk Department of Earth Science, Faculty of Earth and Life Sciences, VU University Amsterdam, Boelelaan 1085, 1081 HV Amsterdam, the NetherlandsSearch for more papers by this authorLianhong Gu, Lianhong Gu Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USASearch for more papers by this authorNiall Hanan, Niall Hanan Geographic Information Science Center of Excellence (GIScCE), South Dakota State University, 1021 Medary Ave., Wecota Hall 506B, Brookings, SD 57007-3510, USASearch for more papers by this authorCarole Helfter, Carole Helfter Centre for Ecology and Hydrology (CEH), Bush Estate, Penicuik, Midlothian, Scotland EH26 0QB, UKSearch for more papers by this authorTakashi Hirano, Takashi Hirano Hokkaido University N9, W9, Kita-ku, Sapporo, Hokkaido, 060-8589, JapanSearch for more papers by this authorDavid Y. Hollinger, David Y. Hollinger USDA Forest Service, Northern Research Station, Durham, NH 03824, USASearch for more papers by this authorMike B. Jones, Mike B. Jones Botany Department, Trinity College of Dublin, Dublin, IrelandSearch for more papers by this authorGerard Kiely, Gerard Kiely Civil and Environmental Engineering Department, University College Cork, Cork, IrelandSearch for more papers by this authorThomas E. Kolb, Thomas E. Kolb School of Forestry, Northern Arizona University, Flagstaff, AZ 86001, USASearch for more papers by this authorWerner L. Kutsch, Werner L. Kutsch Johann Heinrich von Thünen-Institute (vTI), Institute for Climate Research, Braunschweig, GermanySearch for more papers by this authorPeter Lafleur, Peter Lafleur Department of Geography, Trent University, Peterborough, ON K9J 7B8, CanadaSearch for more papers by this authorDavid M. Lawrence, David M. Lawrence National Center for Atmospheric Research, Boulder, CO 80305, USASearch for more papers by this authorLinghao Li, Linghao Li State Key laboratory of Vegetation and Environmental Changes, Institute of Botany, Chinese Academy of SciencesSearch for more papers by this authorAnders Lindroth, Anders Lindroth Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, SwedenSearch for more papers by this authorMarcy Litvak, Marcy Litvak Biology Department, University of New Mexico, Albuquerque, NM 87131-001, USASearch for more papers by this authorDenis Loustau, Denis Loustau INRA, UR1263 EPHYSE, F-33140, Villenave d’Ornon, FranceSearch for more papers by this authorMagnus Lund, Magnus Lund Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, SwedenSearch for more papers by this authorMichal Marek, Michal Marek Institute of Systems Biology and Ecology, Academy of Sciences of the Czech Republic, Poříčí3b, CZ-60300 Brno, Czech RepublicSearch for more papers by this authorTimothy A. Martin, Timothy A. Martin University of Florida, Gainesville, FL 32611, USASearch for more papers by this authorGiorgio Matteucci, Giorgio Matteucci National Research Council, Institute of Agroenvironmental and Forest Biology, 00015 Monterotondo Scalo (RM), ItalySearch for more papers by this authorMirco Migliavacca, Mirco Migliavacca European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, ItalySearch for more papers by this authorLeonardo Montagnani, Leonardo Montagnani Servizi Forestali, Agenzia per l’Ambiente, Provincia Autonoma di Bolzano, 39100, Bolzano, Italy Faculty of Science and Technology, Free University of Bolzano, Piazza Università 1, 39100 Bolzano, ItalySearch for more papers by this authorEddy Moors, Eddy Moors ESS-CC, Alterra, Wageningen UR, PO Box 47, 6700 AA Wageningen, The Netherlands NLSearch for more papers by this authorJ. William Munger, J. William Munger Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, 02138, USASearch for more papers by this authorAsko Noormets, Asko Noormets North Carolina State University/USDA Forest Service, Southern Global Change Program, Raleigh, NC, 27606, USASearch for more papers by this authorWalter Oechel, Walter Oechel Department of Biology, San Diego State University, San Diego, CA 92182-4614, USASearch for more papers by this authorJanusz Olejnik, Janusz Olejnik Meteorology Department, Poznan University of Life Sciences (PULS), 60-667 Poznan, PolandSearch for more papers by this authorKyaw Tha Paw U, Kyaw Tha Paw U Atmospheric Science Group, LAWR, UC Davis, Davis, CA 95616, USASearch for more papers by this authorKim Pilegaard, Kim Pilegaard Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. 49, DK-4000 Roskilde, DenmarkSearch for more papers by this authorSerge Rambal, Serge Rambal DREAM, CEFE, CNRS, UMR5175, 1919 route de Mende, F-34293 Montpellier, Cedex 5, FranceSearch for more papers by this authorAntonio Raschi, Antonio Raschi CNR – Instituto di Biometeorologia (IBIMET), Via Giovanni Caproni 8, 50145 Firenze, ItalySearch for more papers by this authorRussell L. Scott, Russell L. Scott USDA-ARS Southwest Watershed Research Center, Tucson, AZ 85719, USASearch for more papers by this authorGünther Seufert, Günther Seufert European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, ItalySearch for more papers by this authorDonatella Spano, Donatella Spano Department of Economics and Woody Plant Ecosystems, University of Sassari, Sassari, ItalySearch for more papers by this authorPaul Stoy, Paul Stoy Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, USASearch for more papers by this authorMark A. Sutton, Mark A. Sutton USDA Forest Service, Northern Research Station, Durham, NH 03824, USASearch for more papers by this authorAndrej Varlagin, Andrej Varlagin A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Lenisky pr., 33 Moscow, 119071, RussiaSearch for more papers by this authorTimo Vesala, Timo Vesala Department of Physics, FI-00014, University of Helsinki, FinlandSearch for more papers by this authorEnsheng Weng, Ensheng Weng Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorGeorg Wohlfahrt, Georg Wohlfahrt University of Innsbruck, Institute of Ecology Sternwartestr 15, Innsbruck 6020, AustriaSearch for more papers by this authorBai Yang, Bai Yang Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USASearch for more papers by this authorZhongda Zhang, Zhongda Zhang Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USASearch for more papers by this authorXuhui Zhou, Xuhui Zhou Institute of Global Environmental Change Research, Fudan University, Shanghai, ChinaSearch for more papers by this author First published: 07 March 2012 https://doi.org/10.1111/j.1469-8137.2012.04095.xCitations: 75 Author for correspondence: Shuli Niu Tel: +1 405 325 8578 Email: [email protected] AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Summary • It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. • Here, we compiled data from 169 globally distributed sites of eddy covariance and quantified the temperature response functions of net ecosystem exchange (NEE), an ecosystem-level property, to determine whether NEE shows thermal optimality and to explore the underlying mechanisms. • We found that the temperature response of NEE followed a peak curve, with the optimum temperature (corresponding to the maximum magnitude of NEE) being positively correlated with annual mean temperature over years and across sites. Shifts of the optimum temperature of NEE were mostly a result of temperature acclimation of gross primary productivity (upward shift of optimum temperature) rather than changes in the temperature sensitivity of ecosystem respiration. • Ecosystem-level thermal optimality is a newly revealed ecosystem property, presumably reflecting associated evolutionary adaptation of organisms within ecosystems, and has the potential to significantly regulate ecosystem–climate change feedbacks. The thermal optimality of NEE has implications for understanding fundamental properties of ecosystems in changing environments and benchmarking global models. Introduction Ecosystems are represented in most Earth system models in order to simulate the responses and feedbacks of land processes to climate change (Chapin et al., 2002; Friedlingstein et al., 2006). Virtually all ecosystem carbon cycle models use temperature response functions that have been developed from our understanding of biochemical processes of enzymes and/or physiological processes of leaf photosynthesis and organic matter decomposition (Enquist et al., 2003; Friedlingstein et al., 2006) because we lack essential knowledge about ecosystem-level responses to temperature change. The integrated response of ecosystem processes to temperature change is influenced by the responses of its constituents, including plants, animals, microbes, and their interactions. It is well documented that plants (Mooney et al., 1978; Berry & Bjorkman, 1980; Atkin & Tjoelker, 2003), animals (Parmesan, 2006), and microbes (Bradford et al., 2008) acclimate and/or adapt to prevailing environmental conditions in a way that can optimize their functioning under varying temperatures, which is collectively termed optimality (Parker & Maynard Smith, 1990). Thus, we hypothesize that the integrated response of an ecosystem, as an assemblage of interacting organisms, might also demonstrate thermal optimality under temperature change (Loreau, 2010). Nevertheless, thermal optimality at the ecosystem level has not yet been carefully examined. Net ecosystem exchange (NEE) of carbon dioxides is an ecosystem process that reflects the balance of gross primary productivity (GPP) and ecosystem respiration (Re), and is often used to approximate net ecosystem productivity (NEP = −NEE)(Chapin et al., 2006). Previous studies have shown that plant photosynthesis and GPP can acclimate to temperature change via an increase in optimum temperature in a warmer environment (Mooney et al., 1978; Baldocchi et al., 2001; Niu et al., 2008). It has also been documented that Re responds exponentially to temperature as long as there is no soil water limitation (Law et al., 1999), and its temperature sensitivity (Q10) decreases in a warmer environment, a process also described as temperature acclimation (Lloyd & Taylor, 1994; Luo et al., 2001; Tjoelker et al., 2008; Piao et al., 2010). The temperature acclimation of either GPP or Re can lead to changes in the temperature response of NEP. As illustrated in the conceptual Fig. 1, if GPP acclimates to temperature by increasing its optimum temperature in a warmer environment while Re stays unchanged (Fig. 1a), the optimum temperature of NEP at the maximum differences between GPP and Re may also shift upward. Alternatively, if Re acclimates to temperature with decreasing Q10 at higher temperature, while GPP stays unchanged (Fig. 1b), the optimum temperature of NEE will also increase. If both GPP and Re acclimate, the optimum temperature of NEE will likely increase more than that in the previously described two conditions (Fig. 1c). A recent study suggests thermal adaptation of NEE based on a positive relationship between the optimum temperature of NEE and the average summer temperature across space (Yuan et al., 2011). Still, we do not know yet which of the these possible processes contributes to the shift of optimum temperature of NEE, and whether or not the optimum temperature of NEE shifts over time. Figure 1Open in figure viewerPowerPoint Conceptual figure for the shifts of optimum temperature of net ecosystem productivity (NEP; NEP = −NEE (net ecosystem exchange)) as a result of the changes in optimum temperature of gross primary productivity (GPP) or the temperature sensitivity of respiration. (a) Here it is assumed that in a warmer year or at a warmer site, the optimum temperature of NEP shifts higher owing to a shift of optimum temperature of GPP. In (b) it is assumed that the shifts in the optimum temperature of NEP are the result of the temperature acclimation of Re (decrease of Q10). In (c) it is assumed that the optimum temperature of NEP shifts higher owing to acclimation of both GPP and Re. The dashed curves represent the temperature response curve in a warmer year or at a warmer site. The vertical lines refer to the maximum NEP. With the advent of eddy-covariance measurements of NEE, together with detailed meteorological variables (Baldocchi et al., 2001), it has become possible to characterize the ecosystem-level temperature response. In this study, we quantified temperature responses of NEE to determine whether NEE exhibits thermal optimality over time and space, and we further explored the underlying mechanisms. Here, we define acclimation as short-term reversible adjustments of NEE over time and adaptation as geographical changes which are the result of long-term genetic and species compositional changes in ecosystems and the physiological adjustment of those organisms to the prevailing environment. The thermal optimum of NEE and its acclimation and adaptation together are described as thermal optimality. Thermal optimality of whole ecosystem carbon exchange is here assumed to represent ensemble responses of multiple temperature optima of productivity, metabolic, and decomposition p