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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 4 | Copyright

Special issue: Freshwater ecosystems in changing permafrost landscapes

Biogeosciences, 13, 1237-1253, 2016
https://doi.org/10.5194/bg-13-1237-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 01 Mar 2016

Research article | 01 Mar 2016

Thermo-erosion gullies boost the transition from wet to mesic tundra vegetation

Naïm Perreault1,2, Esther Lévesque1,2, Daniel Fortier2,3, and Laurent J. Lamarque1,2 Naïm Perreault et al.
  • 1Département des sciences de l'environnement, Université du Québec à Trois-Rivières, Trois-Rivières, QC, G9A 5H7, Canada
  • 2Centre d'études nordiques, Université Laval, Québec, QC, G1V 0A6, Canada
  • 3Département de géographie, Université de Montréal, Montréal, QC, H2V 2B8, Canada

Abstract. Continuous permafrost zones with well-developed polygonal ice-wedge networks are particularly vulnerable to climate change. Thermo-mechanical erosion can initiate the development of gullies that lead to substantial drainage of adjacent wet habitats. How vegetation responds to this particular disturbance is currently unknown but has the potential to significantly disrupt function and structure of Arctic ecosystems. Focusing on three major gullies of Bylot Island, Nunavut, we estimated the impacts of thermo-erosion processes on plant community changes. We explored over 2years the influence of environmental factors on plant species richness, abundance and biomass in 62 low-centered wet polygons, 87 low-centered disturbed polygons and 48 mesic environment sites. Gullying decreased soil moisture by 40% and thaw-front depth by 10cm in the center of breached polygons within less than 5years after the inception of ice wedge degradation, entailing a gradual yet marked vegetation shift from wet to mesic plant communities within 5 to 10years. This transition was accompanied by a five times decrease in graminoid above-ground biomass. Soil moisture and thaw-front depth changed almost immediately following gullying initiation as they were of similar magnitude between older (>5years) and recently (<5years) disturbed polygons. In contrast, there was a lag-time in vegetation response to the altered physical environment with plant species richness and biomass differing between the two types of disturbed polygons. To date (10years after disturbance), the stable state of the mesic environment cover has not been fully reached yet. Our results illustrate that wetlands are highly vulnerable to thermo-erosion processes, which drive landscape transformation on a relative short period of time for High Arctic perennial plant communities (5 to 10years). Such succession towards mesic plant communities can have substantial consequences on the food availability for herbivores and carbon emissions of Arctic ecosystems.

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We investigated the impacts of climate change and thawing permafrost on vegetation dynamics in Bylot Island, Nunavut. The development of gullies has created new drainage systems within the wetlands, promoting the emergence of mesic plants at the expense of hydrophilic ones within 10 years after disturbance inception. The landscape transformation from wet to mesic plant communities can have substantial consequences on food availability for herbivores and methane emissions of Arctic ecosystems.
We investigated the impacts of climate change and thawing permafrost on vegetation dynamics in...
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