Temperate and boreal forests in the Northern Hemisphere cover an area of about 2 × 107 square kilometres and act as a substantial carbon sink (0.6–0.7 petagrams of carbon per year)1. Although forest expansion following agricultural abandonment is certainly responsible for an important fraction of this carbon sink activity, the additional effects on the carbon balance of established forests of increased atmospheric carbon dioxide, increasing temperatures, changes in management practices and nitrogen deposition are difficult to disentangle, despite an extensive network of measurement stations2,3. The relevance of this measurement effort has also been questioned4, because spot measurements fail to take into account the role of disturbances, either natural (fire, pests, windstorms) or anthropogenic (forest harvesting). Here we show that the temporal dynamics following stand-replacing disturbances do indeed account for a very large fraction of the overall variability in forest carbon sequestration. After the confounding effects of disturbance have been factored out, however, forest net carbon sequestration is found to be overwhelmingly driven by nitrogen deposition, largely the result of anthropogenic activities5. The effect is always positive over the range of nitrogen deposition covered by currently available data sets, casting doubts on the risk of widespread ecosystem nitrogen saturation6 under natural conditions. The results demonstrate that mankind is ultimately controlling the carbon balance of temperate and boreal forests, either directly (through forest management) or indirectly (through nitrogen deposition).

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This work was supported by the European Commission (General Directorate XII, CARBO-AGE project in the CARBOEUROPE cluster) and further supported by several national programmes. F.M. was also supported by the MIUR CarboItaly Project and by Società Produttori Sementi (Fondazione Cassa di Risparmio in Bologna) through the ‘Selvicoltura’ project.

Author information

Author notes

    • Giovanni Manca

    Present address: Institute for Environment and Sustainability—Climate Change Unit, Joint Research Center, European Commission, I-21020 Ispra, Italy.


  1. Department of Fruit Tree and Woody Plant Science, University of Bologna, Bologna I-40127, Italy

    • Federico Magnani
  2. School of GeoSciences, University of Edinburgh, Edinburgh EH93JU, UK

    • Maurizio Mencuccini
    • , Paul G. Jarvis
    • , John B. Moncrieff
    • , Mark Rayment
    •  & John Grace
  3. Department of Crop Systems, Forestry and Environmental Sciences, University of Basilicata, Potenza I-85100, Italy

    • Marco Borghetti
    •  & Vanessa Tedeschi
  4. INRA, UR1263 EPHYSE, Villenave d'Ornon F-33883, France

    • Paul Berbigier
    • , Sylvain Delzon
    • , Andrew S. Kowalski
    •  & Denis Loustau
  5. Departement des Sciences Biologiques, University of Québec à Montréal, Montréal, Quebec, H3C 3P8, Canada

    • Frank Berninger
  6. Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden

    • Achim Grelle
  7. Department of Forest Ecology, University of Helsinki, FIN-00014 Helsinki, Finland

    • Pertti Hari
    •  & Pasi Kolari
  8. Department of Physical Geography and Ecosystems Analysis, Lund University, S-223 62 Lund, Sweden

    • Harry Lankreijer
    •  & Anders Lindroth
  9. College of Forestry, Oregon State University, Corvallis, OR 97331, USA

    • Beverly E. Law
  10. Department of Forest Resources and Environment, University of Tuscia, Viterbo I-01100 Italy

    • Giovanni Manca
    •  & Riccardo Valentini


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Reprints and permissions information is available at The authors declare no competing financial interests.

Corresponding author

Correspondence to Federico Magnani.

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  1. 1.

    Supplementary Information 1

    This file contains Supplementary Figures S1-S8 with Legends and Supplementary Figure S1. The Supplementary Figures show N deposition maps; comparison of results based on to model-based interpolation with raw means and maxima; effects of N deposition when considering individual stands; effects of N deposition covariance with temperature, precipitation and site latitude. The Supplementary Table S1 shows detail of data source and integration procedures used in the computation of average C fluxes in forest chronosequences.

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