Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 16
Biogeosciences, 14, 3815–3829, 2017
https://doi.org/10.5194/bg-14-3815-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 3815–3829, 2017
https://doi.org/10.5194/bg-14-3815-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 23 Aug 2017

Research article | 23 Aug 2017

Patterns and controls of inter-annual variability in the terrestrial carbon budget

Barbara Marcolla1, Christian Rödenbeck2, and Alessandro Cescatti3 Barbara Marcolla et al.
  • 1Fondazione Edmund Mach, IASMA Research and Innovation Centre, Sustainable Agro-ecosystems and Bioresources Department, 38010 San Michele all'Adige, Trento, Italy
  • 2Max Planck Institute for Biogeochemistry, 07745 Jena, Germany
  • 3European Commission, Joint Research Centre, Directorate for Sustainable Resources, 21027 Ispra (VA), Italy

Abstract. The terrestrial carbon fluxes show the largest variability among the components of the global carbon cycle and drive most of the temporal variations in the growth rate of atmospheric CO2. Understanding the environmental controls and trends of the terrestrial carbon budget is therefore essential to predict the future trajectories of the CO2 airborne fraction and atmospheric concentrations. In the present work, patterns and controls of the inter-annual variability (IAV) of carbon net ecosystem exchange (NEE) have been analysed using three different data streams: ecosystem-level observations from the FLUXNET database (La Thuile and 2015 releases), the MPI-MTE (model tree ensemble) bottom–up product resulting from the global upscaling of site-level fluxes, and the Jena CarboScope Inversion, a top–down estimate of surface fluxes obtained from observed CO2 concentrations and an atmospheric transport model. Consistencies and discrepancies in the temporal and spatial patterns and in the climatic and physiological controls of IAV were investigated between the three data sources. Results show that the global average of IAV at FLUXNET sites, quantified as the standard deviation of annual NEE, peaks in arid ecosystems and amounts to  ∼  120 gC m−2 y−1, almost 6 times more than the values calculated from the two global products (15 and 20 gC m−2 y−1 for MPI-MTE and the Jena Inversion, respectively). Most of the temporal variability observed in the last three decades of the MPI-MTE and Jena Inversion products is due to yearly anomalies, whereas the temporal trends explain only about 15 and 20 % of the variability, respectively. Both at the site level and on a global scale, the IAV of NEE is driven by the gross primary productivity and in particular by the cumulative carbon flux during the months when land acts as a sink. Altogether these results offer a broad view on the magnitude, spatial patterns and environmental drivers of IAV from a variety of data sources that can be instrumental to improve our understanding of the terrestrial carbon budget and to validate the predictions of land surface models.

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Patterns and controls of the inter-annual variability of carbon net ecosystem exchange were analysed using three different data streams: ecosystem-level observations (FLUXNET database), a global upscaling of site-level fluxes (MPI-MTE), and a top–down estimate of fluxes (Jena CarboScope Inversion). Consistencies and discrepancies in the temporal and spatial patterns and in the climatic and physiological controls of the inter-annual variability were investigated for the three data sources.
Patterns and controls of the inter-annual variability of carbon net ecosystem exchange were...
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