Plant Traits are Key Determinants in Buffering the Meteorological Sensitivity of Net Carbon Exchanges of Arctic Tundra

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Abstract

The climate sensitivity of carbon (C) cycling in Arctic terrestrial ecosystems is a major unknown in the Earth system. There is a lack of knowledge about the mechanisms that drive the interactions between photosynthesis, respiration, and changes in C stocks across full annual cycles in Arctic tundra. We use a calibrated and validated model (soil-plant-atmosphere; SPA) to estimate net ecosystem exchange (NEE), gross primary production (GPP), ecosystem respiration (Reco), and internal C processing across eight full years. SPA's carbon flux estimates are validated with observational data obtained from the Greenland Ecosystem Monitoring program in West Greenland tundra. Overall, the model explained 73%, 73%, and 50% of the variance in NEE, GPP, and Reco, respectively, and 85% of the plant greenness variation. Flux data highlighted the insensitivity of growing season NEE to interannual meteorological variability, due to compensatory responses of photosynthesis and ecosystem respiration. In this modelling study, we show that this NEE buffering is the case also for full annual cycles. We show through a sensitivity analysis that plant traits related to nitrogen are likely key determinants in the compensatory response, through simulated links to photosynthesis and plant respiration. Interestingly, we found a similar temperature sensitivity of the trait-flux couplings for GPP and Reco, suggesting that plant traits drive the stabilization of NEE. Further, model analysis indicated that wintertime periods decreased the C sink by 60%, mostly driven by litter heterotrophic respiration. This result emphasizes the importance of wintertime periods and allows a more comprehensive understanding of full annual C dynamics.

Detaljer

Författare
  • Efrén López-Blanco
  • Magnus Lund
  • Torben R. Christensen
  • Mikkel P. Tamstorf
  • Thomas L. Smallman
  • Darren Slevin
  • Andreas Westergaard-Nielsen
  • Birger U. Hansen
  • Jakob Abermann
  • Mathew Williams
Enheter & grupper
Externa organisationer
  • Aarhus University
  • University of Edinburgh
  • University of Copenhagen
  • Asiaq Greenland Survey
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Geofysik

Nyckelord

Originalspråkengelska
TidskriftJournal of Geophysical Research - Biogeosciences
StatusPublished - 2018 jul 30
PublikationskategoriForskning
Peer review utfördJa