Wednesday, March 11, 2009

Light Under Snow

Nature Watch
March 11, 2009
By Susan Benson,CNHM Director of Education

Sunlight. Daily, we feel its heat more strongly. It warms our hearts with thoughts of spring. Daylight savings springs ahead to give us more of that terrific sunlight. Even for life under the snow, interesting activities can still occur in the plant and animal world.

No matter how we look at or measure it, there is very little light that reaches underneath the winter snowpack. However, snow can absorb red light most effectively, and blue and blue-green light can reach even greater depths into the snowpack. As the snowpack density increases as snow and ice grains get closer together, more surfaces are created to scatter light and thereby increase light absorption lower into the snowpack. March is a time when this light penetration is often at its highest. It is sunlight absorption that is believed to assist in the spring germination of algae in alpine regions. Research of lichens in polar areas have shown that lichens can absorb water from snow and photosynthesize even in temperatures below 14 degrees Fahrenheit. Conifers have been observed taking in water during the winter – a study in Norway injected dye into a tree just above the snow surface, and found water moving upward. Dye has also been observed moving through roots of a silver birch that was in solid, frozen soil. Scientists still are not sure if the water was absorbed from frozen soil or if there are other ways in which this water movement occurs. Finally, seed germination of many plant species can occur even under the snow. This plant germination leads to some interesting events in the animal world as well.

Winter breeding can occur for some of our small mammals that live in the world under the snow (the subnivean layer.) Although having young might seem strange in the winter, this event might be tied to plant-animal interactions. As seeds germinate under the snow, gibberellic acid, a plant growth hormone is found inside those seeds. It is possible that the stimulus for winter mammal breeding might come from these seeds as they are eaten by an animal. All of this can happen from just a little more sun!

This information brings some new thoughts. Are plants under the snow that seem to still be green in the spring photosynthesize throughout the winter? For animals that never go through daylight savings changes, how do the lower light levels under the snow surface affect daily activity patterns? These are questions for the ecologists to continue to find answers. In the meantime, we can focus on getting outdoors and enjoying that sun!

Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M or on the web at to learn more about exhibits and programs.

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