Mountain Ecology and the Immeasurable Importance of Snow

By Teralene Foxx

SNOW!  We love it and we grumble about it.  We love it because it provides us recreation and a beautiful landscape.  We grumble about it because of slick roads, slippery sidewalks, weighted down trees, and cold.  After years of little or no snow, I have a sense of relief when snow is blanketing the mountain again and hopefully there will be fewer fires. Skiers are relishing in snow covered runs, exclaiming “it’s fabulous.” Snow is an amazing gift of nature and one we take for granted.  But after years of drought, I throw out my negative thoughts about snow and ask “What is the real importance of snow to an ecosystem?”

Ecologically in the Northern Hemisphere, snow is important.  Rain can dampen the earth but snow provides for recharging underground aquifers and streamflow.  The aquifers store trillions of gallons of freshwater used for drinking water.  Streamflow in an arid environment is important to recreation, agriculture, and drinking water.  In some western states snow can make up 80% of the annual precipitation.

I wonder and marvel at the importance of snow. Long ago in High School my favorite biology teacher commented on the whiteness of now.  It coats everything in a fresh white blanket.  We yearn for “White Christmas” and the weatherman will call it the “white stuff.”  So why white?  She made me curious.

Here is the scientific explanation: “Snow reflects all the colors; no it doesn’t absorb, transmit, or scatter any single color or wavelength more than any other. The “color” of all the light wavelengths combined equally is white.”

But for me as an ecologist, I really want to know how snow makes a difference to the ecosystem and all its creatures.  For some I know that snow can be a harsh environment and lead to death. But for every negative in the environment there is a positive. So what is it?

 Snow plays a role in temperature regulation. Snow cover reduces net radiation and acts as a heat sink. It inhibits soil warming until the snow melts but is a good insulator keeping the soil temperature near 32 degrees Ferenheight . 

We often think of winter is a time when everything is dormant or dead.  But our coniferous forests still photosynthesize on warm days and life goes on beneath the snow cover.  Insects, fungi, and mammals busily carry on their actives because of the insulating properties of snow.  Plants covered with snow are protected from drying out. 

Snowpack that accumulates throughout the winter insulates the soil keeping generally unfrozen.  This allows the unfrozen soil to absorb water from melting snow.  In the Eastern states, a ten-inch snowpack covering one acre can hold 30,000 gallons of water! (extension.psu.edu). The humidity of the snow/soil  environment provides a “greenhouse” effect allowing plants to photosynthesize and grow even before the snow is melted. 

The insulating power of snow is also important in other ways.  Without snowpack, very cold temperatures can freeze the soil deeper and deeper.  Root systems within the frozen zone can be damaged, weakening or killing the plant. The milder temperatures and sun warm the exposed and frozen soil causing heaving and root breakage. 

Studies done at the Hubbard Brook Experimental Forest in New Hampshire found that forest productivity forest increased with snow cover.  Without the insulating cover deciduous trees didn’t take up nutrients or water as quickly as those where there was a good snow cover.

The temperature regulation provided by snow is important in the annual growing season and the possibility of fire during the growing season, denuding acres of land of trees changing the dynamics of the ecosystem.  No snow means higher temperatures to the soil and drying  vegetation during the winter months. Studies have shown that there is a correlation with fire and drought.  Within a dry environment, the downed woody and grass material can ignite and the fire can spread rapidly.  But the spread of the fire will also depend on the dryness of the standing vegetation.  The moisture of fuels can change some with rain but the slow percolation of snow melt, the loss of the insulation of soil and vegetation by snow is even more important.  Using LANL’s Weather Machine, Figure 1 illustrates the snowfall the winter before our major fires. The average annual precipitation for the Los Alamos area is 18.86 inches of rainfall and 56 inches of snowfall.  Note during each of these periods the snowfall was significantly lower.

Another advantage to snowpack is to small animals.  Voles, mice and other critters are protected from severe temperatures.  The zone between the snow and the soil is called the subnivean zone. This zone is not solid because vegetation creates air-pockets.  The snow insulates and keeps the temperature around 32 degrees, when the surface temperatures may be much lower.  The small animals, not only are protected from predators, biting wind, and cold temperatures but can access their stored food.  The subnivean zone allows them to make tunnels connecting the air pockets formed under the snow.  Other animals, like the fox, are adapted to hear these small creatures in their tunnels and the pounce.

Because of winter weather, some animals hibernate, others migrate, but others adapt to the snowy environment.  In our mountain area, pikas busily store food during the summer, but, in the winter they are deep in tunnels beneath the snow and rocks giving them access to their stored food.

Some facts about snow:

  • Glaciers cover 10% of the planet’s land area.
  • In the Northern Hemisphere, snow falls each year on one square mile out of two.
  • In the west 75% of the water used for irrigation comes from snow.
  • Snow powers the great rivers: the Colorado, the Rio Grande, the Columbia, the Missouri
  • Snow forms around particulates in the atmosphere and drags it to the ground, cleansing the atmosphere. 

Water—rain, snow, rivers, ponds are the lifeblood of the West. John Wesley Powel l said: “In the whole region, land as mere land is of no value.  What is really valuable is the water privilege.” 

So next time we grumble about shoveling snow or driving on slippery roads, let’s remember that snow is amazing and provides for life in this arid land.

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