Snowfall insulates soil, BU research suggests

Milder winters and a decrease in snowfall due to rising temperatures may cause a decline in soil quality, air quality, tree health and human health, according to a study published Friday by researchers at Boston University.

Researchers in ecosystem ecology, biogeochemistry and global change at BU found snowfall decline could have a lasting effect on our ecosystem.

“Climate models predict that air temperatures will continue to rise and the depth and duration of snow in New England will continue to shrink,” said Pamela Templer, a professor of biology at BU and one of the study’s primary researchers.

According to the study’s research summary, snow acts like a blanket that conserves the temperature of the soil and the living things within, preventing them from being exposed to harsh winter conditions.

“Snow is an insulator,” the research summary stated. “When the snow pack accumulates to sufficient depths, the soil beneath it can remain unfrozen, even when air temperatures are below freezing.”

Due to climate change, air temperatures have increased, causing the amount of snow accumulation to decline, Templer said. The freezing of soil leads to nitrogen runoff that may pollute nearby waterways and pose a health risk to humans.

“Snow insulates all of the living things in soil during winter,” Templer said. “Nitrogen is an essential nutrient for all living things, but if large amounts of nitrogen move into streams and rivers it can further damage trees, acidify stream water and lead to fish mortality and at really high concentrations, can be harmful to human health.”

The researchers conducted a two-year experiment by shoveling snow off research plots in New Hampshire in order to expose the soil to cold temperatures and determine the impact of soil freezing, the research summary stated.

The experiment simulated the effects of a warmer winter. Researchers observed that the exposed soil reached temperatures as much as 10 degrees Celcius lower than the temperatures of soil covered by snow.

This change in ground temperature would cause the soil to freeze and stay frozen long into the changing seasons, Templer said.

“Soils do not typically freeze if they are covered by at least eight inches of snow,” she said. “Taking away snow exposed soils to cold winter temperatures and led to deep freezing of soil.”

As the researchers expected, a smaller amount of snow in their experimental plots caused soil to freeze, which lead to root damage, a decrease in the amount of nitrogen taken in by trees, and an increase in the amount of nitrogen in waterways, Templer said.

“Biota living in soil — plant roots, microbes, insects — rely on snow to insulate them in winter,” Templer said. “Without snow, soils freeze and damage these organisms.”

Researchers have predicted that as air temperatures rise, snow depth and duration in New England will continue to decrease, Templer said.

Templer and her team plan to follow up their recent experiment by examining the effects of warming the soil after it has been frozen.

“We will conduct a new climate change experiment,” Templer said. “The idea is that we take away snow in winter by shoveling as we did in the past, and in the summer we are going to warm the soil continually by 5 degrees Celsius [to] see if the damage gets offset by warmer soil in the summer.”

Templer said climate change was a current and pressing issue.

“We need to educate the public about the implications for climate change,” she said. “Our ecosystems and economy are already being affected by a smaller winter snowpack.”


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