Winter respiratory C losses provide explanatory power for net ecosystem productivity

M. Haeni*, R. Zweifel, W. Eugster, A. Gessler, S. Zielis, C. Bernhofer, A. Carrara, T. Grünwald, K. Havránková, B. Heinesch, M. Herbst, A. Ibrom, A. Knohl, F. Lagergren, B. E. Law, M. Marek, G. Matteucci, J. H. McCaughey, S. Minerbi, L. MontagnaniE. Moors, J. Olejnik, M. Pavelka, K. Pilegaard, G. Pita, A. Rodrigues, M. J. Sanz Sánchez, M. J. Schelhaas, M. Urbaniak, R. Valentini, A. Varlagin, T. Vesala, C. Vincke, J. Wu, N. Buchmann

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Accurate predictions of net ecosystem productivity (NEPc) of forest ecosystems are essential for climate change decisions and requirements in the context of national forest growth and greenhouse gas inventories. However, drivers and underlying mechanisms determining NEPc (e.g., climate and nutrients) are not entirely understood yet, particularly when considering the influence of past periods. Here we explored the explanatory power of the compensation day (cDOY)—defined as the day of year when winter net carbon losses are compensated by spring assimilation—for NEPc in 26 forests in Europe, North America, and Australia, using different NEPc integration methods. We found cDOY to be a particularly powerful predictor for NEPc of temperate evergreen needleleaf forests (R2 = 0.58) and deciduous broadleaf forests (R2 = 0.68). In general, the latest cDOY correlated with the lowest NEPc. The explanatory power of cDOY depended on the integration method for NEPc, forest type, and whether the site had a distinct winter net respiratory carbon loss or not. The integration methods starting in autumn led to better predictions of NEPc from cDOY then the classical calendar method starting 1 January. Limited explanatory power of cDOY for NEPc was found for warmer sites with no distinct winter respiratory loss period. Our findings highlight the importance of the influence of winter processes and the delayed responses of previous seasons' climatic conditions on current year's NEPc. Such carry-over effects may contain information from climatic conditions, carbon storage levels, and hydraulic traits of several years back in time.

Original languageEnglish
Pages (from-to)243-260
Number of pages18
JournalJournal of Geophysical Research: Biogeosciences
Issue number1
Publication statusPublished - 1 Jan 2017


  • carbon sink
  • carbon source
  • CO exchange
  • eddy covariance
  • growing season length
  • winter respiration


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