Preprints
https://doi.org/10.5194/bg-2021-169
https://doi.org/10.5194/bg-2021-169

  28 Jun 2021

28 Jun 2021

Review status: this preprint is currently under review for the journal BG.

Nitrogen restricts future treeline advance in the sub-arctic

Adrian Gustafson1,2, Paul A. Miller1,2, Robert Björk4,5, Stefan Olin1, and Benjamin Smith1,3 Adrian Gustafson et al.
  • 1Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62 Lund, Sweden
  • 2Center for Environmental and Climate Science, Lund University, Sölvegatan 37, 223 62, Lund, Sweden
  • 3Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia
  • 4Department of Earth Sciences, University of Gothenburg, P.O. Box 460, SE-40530 Gothenburg, Sweden
  • 5Gothenburg Global Biodiversity Centre, P.O. Box 461, SE-405 30 Gothenburg, Sweden

Abstract. Arctic environmental change has induced shifts in high latitude plant community composition and stature with impli-cations for Arctic carbon cycling and energy exchange. Two major components of high latitude ecosystems undergoing change is the advancement of trees into treeless tundra and the increased abundance and size of shrubs. How future changes in key climatic and environmental drivers will affect distributions of major ecosystem types is an active area of research. Dynamic Vegetation Models (DVMs) offer a way to investigate multiple and interacting drivers of vegeta-tion distribution and ecosystem function. We employed the LPJ-GUESS DVM over a subarctic landscape in northern Sweden, Torneträsk. Using a highly resolved climate dataset we downscaled CMIP5 climate data from three Global Climate Models and two 21st century future scenarios (RCP2.6 and RCP8.5) to investigate future impacts of climate change on these ecosystems. We also performed three model experiments where we factorially varied drivers (climate, nitrogen deposition and [CO2]) to disentangle the effects of each on ecosystem properties and functions. We found that treelines could advance by between 45 and 195 elevational meters in the landscape until the year 2100, depending on the scenario. Temperature was a strong, but not the only, driver of vegetation change. Nitrogen availability was identi-fied as an important modulator of treeline advance. While increased CO2 fertilisation drove productivity increases it did not result in any range shifts of trees. Treeline advance was realistically simulated without any temperature depend-ence on growth, but biomass was overestimated. As nitrogen was identified as an important modulator of treeline ad-vance, we support the idea that accurately representing plant-soil interactions in models will be key to future predic-tions Arctic vegetation change.

Adrian Gustafson et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Solid, interesting study; needs some further discussion of omitted processes and improved presentation', Anonymous Referee #1, 28 Jul 2021
    • AC1: 'Reply on RC1', Adrian Gustafson, 10 Sep 2021
  • RC2: 'Comment on bg-2021-169', Ch. Körner, 13 Sep 2021
    • AC2: 'Reply on RC2', Adrian Gustafson, 29 Sep 2021

Adrian Gustafson et al.

Adrian Gustafson et al.

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Short summary
We performed model simulations of vegetation change under historic and climate change scenarios at high spatial resolution. Projected treeline advance continued at the same or increased rates as during our historic simulation. Temperature isolines advanced faster than treelines, revealing a lag in potential vegetation shifts that was modulated by nitrogen availability. At year 2100 our projected treelines had advanced by 45 to 195 elevational meters depending on the scenario.
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