New paper in Biogeosciences: Thermo-erosion gullies boost the transition from wet to mesic tundra vegetation

March 14, 2016 in Article, post by Perreault.N

Field surveys were conducted over two years in the Qarlikturvik valley of Bylot Island, NU to assess the impacts of thermo-erosion gullies on the vegetation of surrounding low-centered wet polygons. Based on 197 sites located around three gullies, plant species richness, plant species abundance and graminoid above-ground biomass of breached polygons were compared to those of two baseline habitats – intact wet polygons and intact mesic environments.

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The inception of ice wedge degradation immediately decreased soil moisture and thaw front depth of breached polygons – as found by Godin et al. (2016) – and the environmental conditions of disturbed polygons thus got closer to those of mesic environments. Consequently, we observed a gradual but marked shift in vascular plant community composition within ten years after disturbance, characterized by the emergence of Arctagrostis latifolia and Salix spp. at the expense of hydrophilic species such as Carex aquatilis, Eriophorum scheuchzeri and Dupontia fisheri.

High Arctic wetlands are therefore highly sensitive to thermo-erosion processes, which can rapidly drive the transformation of low-centered wet polygon landscape. The transition towards mesic environments could soon impact food resources of herbivores – which are fond of hydrophilic species – and modify emissions of greenhouse gases.

Interestingly, the latest observations showed that, ten years after disturbance inception, hydrology and thaw regimes of breached polygons have not reached equilibrium with new conditions yet whilst cover of mesic bryophytes and dominant shrubs are still lower than in adjacent intact mesic environments. This paves the way for long-term monitoring studies of permafrost disturbance and recovery of its associated vegetation.

 

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The full story is available here:

Perreault, N., Lévesque, E., Fortier, D. and Lamarque L. J.: Thermo-erosion gullies boost the transition from wet to mesic tundra vegetation, Biogeosciences, 13, 1237-1253, 2016.

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