Net ecosystem exchange of CO 2 with rapidly changing high Arctic landscapes

• Published in: Global Change Biology
• Main Authors: Emmerton, Craig A., St. Louis, Vincent L., Humphreys, Elyn R., Gamon, John A., Barker, Joel D., Pastorello, Gilberto Z.
• Other Authors: Natural Sciences and Engineering Research Council of Canada, Natural Resources Canada, Aboriginal Affairs and Northern Development Canada, University of Alberta
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Climate change
• Online Access: http://dx.doi.org/10.1111/gcb.13064; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.13064; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.13064

Abstract High Arctic landscapes are expansive and changing rapidly. However, our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange ( NEE ) of CO 2 with polar semidesert and meadow wetland landscapes at the highest latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI ) to evaluate the effectiveness of upscaling local to regional NEE . During the growing season, the dry polar semidesert landscape was a near‐zero sink of atmospheric CO 2 ( NEE : −0.3 ± 13.5 g C m −2 ). A nearby meadow wetland accumulated over 300 times more carbon ( NEE : −79.3 ± 20.0 g C m −2 ) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southerly latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO 2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO 2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on‐site was low (mean: 0.120–0.157) and similar to satellite measurements (mean: 0.155–0.163). However, weak plant growth resulted in poor satellite NDVI – NEE relationships and created challenges for remotely detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote sensing; however, high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases enough to offset poor soil moisture retention, climate‐related changes to productivity on polar semideserts may be restricted.