Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations1. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage—increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands2,3. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree4,5,6,7, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level8,9,10 and stand-level10 productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation11 and plant senescence12.

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We thank the hundreds of people who have established and maintained the forest plots and their associated databases; M. G. Ryan for comments on the manuscript; C. D. Canham and T. Hart for supplying data; C. D. Canham for discussions and feedback; J. S. Baron for hosting our workshops; and Spain’s Ministerio de Agricultura, Alimentación y Medio Ambiente (MAGRAMA) for granting access to the Spanish Forest Inventory Data. Our analyses were supported by the United States Geological Survey (USGS) John Wesley Powell Center for Analysis and Synthesis, the USGS Ecosystems and Climate and Land Use Change mission areas, the Smithsonian Institution Global Earth Observatory—Center for Tropical Forest Science (CTFS), and a University of Nebraska-Lincoln Program of Excellence in Population Biology Postdoctoral Fellowship (to N.G.B.). In addition, X.W. was supported by National Natural Science Foundation of China (31370444) and State Key Laboratory of Forest and Soil Ecology (LFSE2013-11). Data collection was funded by a broad range of organizations including the USGS, the CTFS, the US National Science Foundation, the Andrews LTER (NSF-LTER DEB-0823380), the US National Park Service, the US Forest Service (USFS), the USFS Forest Inventory and Analysis Program, the John D. and Catherine T. MacArthur Foundation, the Andrew W. Mellon Foundation, MAGRAMA, the Council of Agriculture of Taiwan, the National Science Council of Taiwan, the National Natural Science Foundation of China, the Knowledge Innovation Program of the Chinese Academy of Sciences, Landcare Research and the National Vegetation Survey Database (NVS) of New Zealand, the French Fund for the Global Environment and Fundación ProYungas. This paper is a contribution from the Western Mountain Initiative, a USGS global change research project. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USA government.

Author information

Author notes

    • N. G. Beckman
    •  & N. Rüger

    Present addresses: Mathematical Biosciences Institute, Ohio State University, Columbus, Ohio 43210, USA (N.G.B.); German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, 04103 Leipzig, Germany (N.R.).


  1. US Geological Survey, Western Ecological Research Center, Three Rivers, California 93271, USA

    • N. L. Stephenson
    •  & A. J. Das
  2. Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama

    • R. Condit
    • , N. Rüger
    •  & S. P. Hubbell
  3. School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA

    • S. E. Russo
    •  & N. G. Beckman
  4. Department of Forest and Ecosystem Science, University of Melbourne, Victoria 3121, Australia

    • P. J. Baker
  5. Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK

    • D. A. Coomes
  6. Department of Geography, University College London, London WC1E 6BT, UK

    • E. R. Lines
  7. School of Botany, University of Melbourne, Victoria 3010, Australia

    • W. K. Morris
  8. Spezielle Botanik und Funktionelle Biodiversität, Universität Leipzig, 04103 Leipzig, Germany

    • N. Rüger
  9. Jardín Botánico de Medellín, Calle 73, No. 51D-14, Medellín, Colombia

    • E. Álvarez
  10. Instituto de Ecología Regional, Universidad Nacional de Tucumán, 4107 Yerba Buena, Tucumán, Argentina

    • C. Blundo
    • , H. R. Grau
    •  & A. Malizia
  11. Research Office, Department of National Parks, Wildlife and Plant Conservation, Bangkok 10900, Thailand

    • S. Bunyavejchewin
  12. Department of Botany and Plant Physiology, Buea, Southwest Province, Cameroon

    • G. Chuyong
  13. Smithsonian Institution Global Earth Observatory—Center for Tropical Forest Science, Smithsonian Institution, PO Box 37012, Washington, DC 20013, USA

    • S. J. Davies
    •  & D. Kenfack
  14. Universidad Nacional de Colombia, Departamento de Ciencias Forestales, Medellín, Colombia

    • Á. Duque
  15. Wildlife Conservation Society, Kinshasa/Gombe, Democratic Republic of the Congo

    • C. N. Ewango
    •  & J.-R. Makana
  16. Unité Mixte de Recherche—Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Université de la Réunion/CIRAD, 97410 Saint Pierre, France

    • O. Flores
  17. School of Environmental and Forest Sciences, University of Washington, Seattle, Washington 98195, USA

    • J. F. Franklin
  18. State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China

    • Z. Hao
    •  & X. Wang
  19. Department of Forest Ecosystems and Society, Oregon State University, Corvallis, Oregon 97331, USA

    • M. E. Harmon
    •  & R. J. Pabst
  20. Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California 90095, USA

    • S. P. Hubbell
  21. Department of Life Science, Tunghai University, Taichung City 40704, Taiwan

    • Y. Lin
  22. Facultad de Ciencias Agrarias, Universidad Nacional de Jujuy, 4600 San Salvador de Jujuy, Argentina

    • L. R. Malizia
  23. Faculty of Forestry, Kasetsart University, ChatuChak Bangkok 10900, Thailand

    • N. Pongpattananurak
  24. Taiwan Forestry Research Institute, Taipei 10066, Taiwan

    • S.-H. Su
  25. Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien 97401, Taiwan

    • I-F. Sun
  26. Sarawak Forestry Department, Kuching, Sarawak 93660, Malaysia

    • S. Tan
  27. Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA

    • D. Thomas
  28. US Geological Survey, Western Ecological Research Center, Arcata, California 95521, USA

    • P. J. van Mantgem
  29. Landcare Research, PO Box 40, Lincoln 7640, New Zealand

    • S. K. Wiser
  30. Forest Ecology and Restoration Group, Department of Life Sciences, University of Alcalá, Alcalá de Henares, 28805 Madrid, Spain

    • M. A. Zavala


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N.L.S. and A.J.D. conceived the study with feedback from R.C. and D.A.C., N.L.S., A.J.D., R.C. and S.E.R. wrote the manuscript. R.C. devised the main analytical approach and wrote the computer code. N.L.S., A.J.D., R.C., S.E.R., P.J.B., N.G.B., D.A.C., E.R.L., W.K.M. and N.R. performed analyses. N.L.S., A.J.D., R.C., S.E.R., P.J.B., D.A.C., E.R.L., W.K.M., E.Á., C.B., S.B., G.C., S.J.D., Á.D., C.N.E., O.F., J.F.F., H.R.G., Z.H., M.E.H., S.P.H., D.K., Y.L., J.-R.M., A.M., L.R.M., R.J.P., N.P., S.-H.S., I-F.S., S.T., D.T., P.J.v.M., X.W., S.K.W. and M.A.Z. supplied data and sources of allometric equations appropriate to their data.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to N. L. Stephenson.

Fitted model parameters for each species have been deposited in USGS’s ScienceBase at http://dx.doi.org/10.5066/F7JS9NFM.

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    Supplementary Information

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