Abstract
Arctic warming is causing substantial compositional, structural, and functional changes in tundra vegetation including shrub and tree-line expansion and densification. However, predicting the carbon trajectories of the changing Arctic is challenging due to interacting feedbacks between vegetation composition and structure, and surface characteristics. We conduct a sensitivity analysis of the current-date to 2100 projected surface energy fluxes, soil carbon pools, and CO2 fluxes to different shrub expansion rates under future emission scenarios (intermediate—RCP4.5, and high—RCP8.5) using the Arctic-focused configuration of E3SM Land Model (ELM). We focus on Trail Valley Creek (TVC), an upland tundra site in the western Canadian Arctic, which is experiencing shrub densification and expansion. We find that shrub expansion did not significantly alter the modeled surface energy and water budgets. However, the carbon balance was sensitive to shrub expansion, which drove higher rates of carbon sequestration as a consequence of higher shrubification rates. Thus, at low shrub expansion rates, the site would become a carbon source, especially under RCP8.5, due to higher temperatures, which deepen the active layer and enhance soil respiration. At higher shrub expansion rates, TVC would become a net CO2 sink under both Representative Concentration Pathway scenarios due to higher shrub productivity outweighing temperature-driven respiration increase. Our simulations highlight the effect of shrub expansion on Arctic ecosystem carbon fluxes and stocks. We predict that at TVC, shrubification rate would interact with climate change intensity to determine whether the site would become a carbon sink or source under projected future climate.
| Original language | English |
|---|---|
| Article number | e2024JG008721 |
| Journal | Journal of Geophysical Research: Biogeosciences |
| Volume | 130 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 2025 |
Funding
TY was funded in part through a FLUXNET Secondment Fellowship. TY and GB were funded by the US Department of Energy (awards DE-SC0021067, DE-SC0023084). Funding for field observations in TVC was provided by the Canada Research Chair (award CRC-2018-00259) and NSERC Discovery Grants Program (award DGPIN-2018-05743) to OS. QZ and WJR were supported by the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation (RUBISCO) Scientific Focus Area. BS and FY were supported by the Next Generation Ecosystem Experiments (NGEE) Arctic project, which is supported by the Office of Biological and Environmental Research in the US Department of Energy's Office of Science. E3SM/ELM tools were obtained from the Energy Exascale Earth System Model project, sponsored by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Earth Systems Model Development Program area of Earth and Environmental System Modeling. We acknowledge support from an NSF AccelNet program (award 2113978) through a FLUXNET secondment award to TY. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. TY was funded in part through a FLUXNET Secondment Fellowship. TY and GB were funded by the US Department of Energy (awards DE‐SC0021067, DE‐SC0023084). Funding for field observations in TVC was provided by the Canada Research Chair (award CRC‐2018‐00259) and NSERC Discovery Grants Program (award DGPIN‐2018‐05743) to OS. QZ and WJR were supported by the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation (RUBISCO) Scientific Focus Area. BS and FY were supported by the Next Generation Ecosystem Experiments (NGEE) Arctic project, which is supported by the Office of Biological and Environmental Research in the US Department of Energy's Office of Science. E3SM/ELM tools were obtained from the Energy Exascale Earth System Model project, sponsored by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Earth Systems Model Development Program area of Earth and Environmental System Modeling. We acknowledge support from an NSF AccelNet program (award 2113978) through a FLUXNET secondment award to TY. Notice: This manuscript has been authored by UT‐Battelle, LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid‐up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ). Oak Ridge National Laboratory is managed by UT‐Battelle, LLC, for the U.S. Department of Energy under contract DE‐AC05‐00OR22725.
Keywords
- Arctic shrubification
- ELM
- carbon budget
- carbon fluxes
- eddy covariance