Exchange of CO2 in Arctic tundra: Impacts of meteorological variations and biological disturbance

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<p>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 analyzed the net ecosystem exchange (NEE) of CO<sub>2</sub> in West Greenland tundra (64°&amp;thinsp;N) across eight snow-free periods in eight consecutive years, and characterized the key processes of net ecosystem exchange, and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO<sub>2</sub>, accumulating &amp;minus;30&amp;thinsp;g C&amp;thinsp;m<sup>&amp;minus;2</sup> on average (range &amp;minus;17 to &amp;minus;41&amp;thinsp;g C&amp;thinsp;m<sup>&amp;minus;2</sup>) during the years 2008&amp;ndash;2015, except 2011 that was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO<sub>2</sub> uptake despite the high inter-annual variability in the timing of snowmelt, start and duration of the growing season. The ranges in annual GPP (&amp;minus;182 to &amp;minus;316&amp;thinsp;g C&amp;thinsp;m<sup>&amp;minus;2</sup>) and Reco (144 to 279&amp;thinsp;g C&amp;thinsp;m<sup>&amp;minus;2</sup>) were >&amp;thinsp;5 fold larger and they were also more variable (Coefficients of variation are 3.6 and 4.1&amp;thinsp;% respectively) than for NEE (0.7&amp;thinsp;%). GPP and Reco were sensitive to insolation and temperatures; and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to climate was a result of the correlated meteorological response of GPP and Reco. During the 2011 anomalous year, the studied ecosystem released 41&amp;thinsp;g C&amp;thinsp;m<sup>&amp;minus;2</sup> as biological disturbance reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling although shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge the forecast of upcoming C states.</p>




López-Blanco, E., Lund, M., Williams, M., Tamstorf, M. P., Westergaard-Nielsen, A., Exbrayat, J. F., … Christensen, T. R. (2017). Exchange of CO2 in Arctic tundra: Impacts of meteorological variations and biological disturbance. Biogeosciences, 14(19), 4467–4483.

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