also allows the formation of a subnivean cavity in which Animal tracks in the snow.
small mammals nest and feed, protected from preda-
Photo: Artis Rams/iStockphoto.com
tors such as foxes and snowy owls. Along streams in late
winter, the subnivean cavity can be as wide as 2 m.
Snow provides a habitat for some “primitive” forms of
life. A relatively abundant and diverse array of micro-or-
ganisms can be found on both seasonal snow cover
48
and
persistent snow on glaciers
49
. These organisms include
algae that can colour the snow red, blue or green, bac-
teria, fungi, diatoms, viruses, rotifers and tardigrades.
On Signy Island, a small subantarctic island, cell num-
bers range from 5000 cells per cubic millimetre for col-
oured snow to 1 to 2 cells per cubic millimetre for clean
snow
49
. The presence of organic matter in and on snow
reduces albedo and results in local melt and accumula-
tion of nutrients.
The fractional snow cover (snow in patches) in the spring
months affects the breeding of certain ground nesting
species, such as waders, ducks and geese (see box on
migratory sandpipers and snow). Fractional snow cover,
particularly associated with small-scale topographical
differences within the landscape, also affects the distri-
bution of plant communities and species. Plant com-
munities that are characteristic of depressions where
snow accumulates have short growing seasons and are
waterlogged after thaw
39
whereas communities on wind-
exposed ridges are more drought tolerant
50
. Traditional
Saami knowledge has described the influence of snow
cover on the vertical distributions of lichens that live on
mountain birch stems in the subarctic; Parmelia olivacea
grows above the winter snow line, whereas Parmeliopsis
ambigua grows below the snow line and is covered by
snow for six months per year
47
.
Snow accumulates debris and chemicals including plant
nutrients and pollutants from the atmosphere. Some of
these, such as atmospheric nitrogen
54
and seeds, ac-
cumulate over the winter and are then released or re-
48 GLOBAL OUTLOOK FOR ICE AND SNOW