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

March 14, 2016 in Article, post

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.

lamarque-bylot-1

lamarque-bylot-2

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.

 

lamarque-bylot-3

 

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.

PDF

New paper in Biogeosciences: Nonlinear thermal and moisture response of ice-wedge polygons to permafrost disturbance increases heterogeneity of high Arctic wetland

March 10, 2016 in Article, post

The floor of the Qalikturvik valley (Bylot Island, NU) is a mosaic ice-wedges polygons. A subtype of polygons named wet polygons are bowl like shaped, which enable moisture from snowmelt and precipitation to concentrate in their centers. These fields of wet polygons can support productive ecological environments, particularly when considering the usually arid nature of the High-Arctic.

Thermal erosion gullying erode and breach the contour (rims) of the bowl-shaped polygons, therefore affecting their capacity to retain moisture and possibly changing the near-surface thermal regime. One gully can breach the rims of hundreds of polygons: at the study site, three dozen gullies were located.

Nearby polygons located near a gully were identified and instrumented; reference and intact polygon characteristics were compared against eroded polygons during 2012-2013. The intact polygon center was saturated following snowmelt and during precipitation events later in summer. The moisture diminished following the thickening of the active-layer and its overall moisture was significantly higher than any disturbed polygons. The thermal regime during 2012-13 for this polygon was similar to another intact polygon. The vegetation in its center was well distributed and relatively uniform (ex: Carex sp.).

On the other hand, disturbed polygons were characterized by varying state for their moisture, ground temperature and vegetation cover. A disturbed polygon could simultaneously be partially dry, partially wet, depending on the severity of the rims breach. The active layer evolution could be similar to an intact polygon or could be significantly thinner. Dry tussocks were present in the centers, underlining the changing moisture state of the polygon, where plants better adapted to the new conditions settled. Therefore in the eroded polygon centers, there was an intra-polygonal variability as there was an heterogeneity in the moisture levels and plant distributions and an inter-polygonal variability (as in not all disturbed polygon were affected in the same way), depending on the severity of the breach, the recharge capability and proximity to the gully.

At the scale of the decade, gullying cause heterogeneity in the landscape with a tendency toward a dryer environment than pre-gullying. Further, gullying affect polygons rims thus the area affected by the erosion exceeds the gully as it affects an entire disturbed polygon.

The paper is available here:

Godin, E.; Fortier, D. & Lévesque, E.
Nonlinear thermal and moisture response of ice-wedge polygons to permafrost disturbance increases heterogeneity of high Arctic wetland
Biogeosciences, 2016, 13, 1439-1452

 

 

New publication

May 5, 2014 in Article, Paper

Eva Stephani and Daniel Fortier collaborated on a new paper recently published in the international journal Cold Regions Science and Technology. The paper is titled “A geosystems approach to permafrost investigations for engineering applications, an example from a road stabilization experiment, Beaver Creek, Yukon, Canada“.
For more information or to get a pdf copy of the paper, contact Eva! (evastephani@golder.com)

Week #1 – Recent Cryosphere papers

January 6, 2014 in Article

Van Wychen, W., et al. (2013). “Glacier velocities and dynamic ice discharge from the Queen Elizabeth Islands, Nunavut, Canada.” Geophysical Research Letters: 2013GL058558.

Van Nieuwenhove, N. and J. P. Briner (2014). “Sea-ice, glaciers and climate dynamics of Baffin Bay and the NW Passage.” Journal of Quaternary Science 29(1): 1-1.

Bouchard, F., et al. (2013). “Vulnerability of shallow subarctic lakes to evaporate and desiccate when snowmelt runoff is low.” Geophysical Research Letters 40(23): 2013GL058635.

Strauss, J., et al. (2013). “The deep permafrost carbon pool of the Yedoma region in Siberia and Alaska.” Geophysical Research Letters 40(23): 2013GL058088. (Open Access)

Wik, M., et al. (2014). “Energy input is primary controller of methane bubbling in subarctic lakes.” Geophysical Research Letters: 2013GL058510.

An, H. and S. J. Noh “High-order averaging method of hydraulic conductivity for accurate soil moisture modeling.” Journal of Hydrology(0). (Early Access)

Kneisel, C., et al. “Application of 3D electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies.” Geomorphology(0). (Early Access)