Resistance and change in a High Arctic ecosystem, NW Greenland: Differential sensitivity of ecosystem metrics to 15 years of experimental warming and wetting

• Published in: Global Change Biology
• Main Authors: Jespersen, Robert Gus, Leffler, Alan Joshua, Väisänen, Maria, Welker, Jeffrey M.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: Arctic; Greenland; Climate change
• Online Access: http://dx.doi.org/10.1111/gcb.16027; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.16027; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gcb.16027; https://onlinelibrary.wiley.com/doi/am-pdf/10.1111/gcb.16027

Abstract Dramatic increases in air temperature and precipitation are occurring in the High Arctic (>70°N), yet few studies have characterized the long‐term responses of High Arctic ecosystems to the interactive effects of experimental warming and increased rain. Beginning in 2003, we applied a factorial summer warming and wetting experiment to a polar semidesert in northwest Greenland. In summer 2018, we assessed several metrics of ecosystem structure and function, including plant cover, greenness, ecosystem CO 2 exchange, aboveground (leaf, stem) and belowground (litter, root, soil) carbon (C) and nitrogen (N) concentrations (%) and pools, as well as leaf and soil stable isotopes (δ 13 C and δ 15 N). Wetting induced the most pronounced changes in ecosystem structure, accelerating the expansion of Salix arctica cover by 370% and increasing aboveground C, N, and biomass pools by 94%–101% and root C, N, and biomass pools by 60%–122%, increases which coincided with enhanced net ecosystem CO 2 uptake. Further, wetting combined with warming enhanced plot‐level greenness, whereas in isolation neither wetting nor warming had an effect. At the plant level, the effects of warming and wetting differed among species and included warming‐linked decreases in leaf N and δ 15 N in S. arctica , whereas leaf N and δ 15 N in Dryas integrifolia did not respond to the climate treatments. Finally, neither plant‐ nor plot‐level C and N allocation patterns nor soil C, N, δ 13 C, or δ 15 N concentrations changed in response to our manipulations, indicating that these ecosystem metrics may resist climate change, even in the longer term. In sum, our results highlight the importance of summer precipitation in regulating ecosystem structure and function in arid parts of the High Arctic, but they do not completely refute previous findings of resistance in some High Arctic ecosystem properties to climate change.