Range shifts in a foundation sedge potentially induce large Arctic ecosystem carbon losses and gains

• Published in: Environmental Research Letters
• Main Authors: Curasi, Salvatore R., Fetcher, Ned, Hewitt, Rebecca E., Lafleur, Peter M., Loranty, Michael M., Mack, Michelle C., May, Jeremy L., Myers-Smith, Isla H., Natali, Susan M., Oberbauer, Steven F., Parker, Thomas C., Sonnentag, Oliver, Vargas Zesati, Sergio A., Wullschleger, Stan D., Rocha, Adrian V.
• Language: unknown
• Published: 2022
• Subjects: 54 ENVIRONMENTAL SCIENCES; Arctic; Eriophorum; Victoria Island
• Online Access: http://www.osti.gov/servlets/purl/1876259; https://www.osti.gov/biblio/1876259; https://doi.org/10.1088/1748-9326/ac6005

Foundation species have disproportionately large impacts on ecosystem structure and function. As a result, future changes to their distribution may be important determinants of ecosystem carbon (C) cycling in a warmer world. We assessed the role of a foundation tussock sedge (Eriophorum vaginatum) as a climatically vulnerable C stock using field data, a machine learning ecological niche model, and an ensemble of terrestrial biosphere models (TBMs). Field data indicated that tussock density has decreased by ~0.97 tussocks per m2 over the past ~38 years on Alaska's North Slope from ~1981 to 2019. This declining trend is concerning because tussocks are a large Arctic C stock, which enhances soil organic layer C stocks by 6.9% on average and represents 745 Tg C across our study area. By 2100, we project that changes in tussock density may decrease the tussock C stock by 41% in regions where tussocks are currently abundant (e.g. -0.8 tussocks per m2 and -85 Tg C on the North Slope) and may increase the tussock C stock by 46% in regions where tussocks are currently scarce (e.g. +0.9 tussocks per m2 and +81 Tg C on Victoria Island). These climate-induced changes to the tussock C stock were comparable to, but sometimes opposite in sign, to vegetation C stock changes predicted by an ensemble of TBMs. Our results illustrate the important role of tussocks as a foundation species in determining future Arctic C stocks and highlight the need for better representation of this species in TBMs.