Exchange of CO 2 in Arctic tundra: impacts of meteorological variations and biological disturbance

• Published in: Biogeosciences
• Main Authors: E. López-Blanco, M. Lund, M. Williams, M. P. Tamstorf, A. Westergaard-Nielsen, J.-F. Exbrayat, B. U. Hansen, T. R. Christensen
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2017
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Greenland; Tundra
• Online Access: https://doi.org/10.5194/bg-14-4467-2017; https://doaj.org/article/75988d6b076340deb35af03c89e6af4c

An improvement in our process-based understanding of carbon (C) exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE) of CO 2 in West Greenland tundra (64° N) across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP) and ecosystem respiration ( R eco ). Overall, the ecosystem acted as a consistent sink of CO 2 , accumulating −30 g C m −2 on average (range of −17 to −41 g C m −2 ) during the years 2008–2015, except 2011 (source of 41 g C m −2 ), which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO 2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (−182 to −316 g C m −2 ) and R eco (144 to 279 g C m −2 ) were > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and R eco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and R eco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and R eco . During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than R eco . With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.