Vegetation as a Melting Bioindicator

The snow cover of the polar regions is an important component of the global climate system, not only because it modifies energy and moisture fluxes between the land surface and the atmosphere, but also because it acts as a reservoir of water in hydrological systems. Over the past few years, several studies have reported decreasing snow thickness at the poles and assessed the consequences of this change in the near future.

These changes can have important effects on ecosystems, especially when the spatial variability of the cover is high, influencing the biogeochemical conditions (examples: moisture, temperature, nutrients) of the underlying soil, as well as vegetation and light. It also controls species distribution, growth phase duration and phenology.

The study highlighted this month was conducted on Signy Island, Antarctica, where snow thickness and area distribution were monitored using a time-lapse camera on a 15 x 20 meter grid over an 8-year period (2009-2017).

Fig. 1- (a) Location of Signy Island; (b) Study área (red dot) and Signy’s Research Station (black dot); (c) Example of a snow grid used in the study.

The results confirmed the high spatial and temporal variability of the snow cover. During the study period, the annual mean snow depth ranged from 5.6 cm (2017) to 11.1 cm (2012), while the maximum daily mean snow depth across the grid ranged from 17.1 cm (2017) to 50.1 cm (2015). Although no temporal trend was visible, a strong correlation with the mean annual air temperature was observed, suggesting that a possible future warming could decrease the snow depth in the area.

In addition, it was also possible to verify the presence of vegetation as a bioindicator of snow thickness, in line with previous studies.

For example, vegetation dominated by Andreaea spp. is associated with thinner snow cover, and this cushion moss community occurs in exposed, dry to wet habitats with intermittent water supply after the end of snow melt in spring. In the thicker snow cover, a moss community dominated by Sanionia uncinata is found, which requires higher water availability, occurring in mesic and hydric habitats.

It was observed that the Usnea dominated lichen vegetation is limited to areas with low snow cover, so it can be confirmed that this plant formation can be indicative of areas with low snow accumulation. In addition, its presence is associated with earlier snow melting, (Fig. 2 – C), since its structure, color and thermal properties favor early melting and delay snow accumulation. 

Fig. 2. Examples of snow distribution at Signy island: (a) Snow tends to accumulate in depressions. Date:  20/02/2013. (b) Snow redistribution by wind tends to lead to accumulation in the presence of obstacles (for example the stake d5 is completely covered by snow). Date: 20/06/2009. (c) Snow located on Usnea lichen formation melts earlier than on other landcover types. Date: 27/10/2015.

The data demonstrates the importance of microtopography and wind direction, as well as the type of ground cover (vegetation), on snow cover patterns, since these factors influence the processes of snow accumulation, redistribution and ablation. It also highlights the importance of spatial monitoring of snow accumulation at a small physical scale in order to predict the future effects of climate change on sensitive terrestrial ecosystems in Antarctica.


Source: Tarca, G., Guglielmin, M., Convey, P., Worland, M. R. & Cannone, N. Small-scale spatial–temporal variability in snow cover and relationships with vegetation and climate in maritime Antarctica. Catena vol. 208 105739 (2022). DOI: 10.1016/j.catena.2021.10573

Author: Márcia Dias