A team of researchers studying snowpack decline found that snowless winters leave trees stunted.
In a series of forest manipulation experiments begun in 2007 at Hubbard Brook Experimental Forest in New Hampshire, researchers led by Andrew Reinmann, an assistant professor at Hunter College, aimed to assess how the changing climate would affect a variety of forest ecosystem processes. So every time it snowed during the first four to six weeks of winter over a five-year period, they removed the snow from four study plots and measured the characteristics of the soil and the mature sugar maples growing there.
“During the growing season, the soil heats up, and then in late fall and early winter, when snow begins to fall, the soil remains relatively warm because the blanket of snow insulates the soil so the warmth is slow to leave,” said Reinmann of the way things have traditionally played out. “Then, when the really cold air of winter comes, it is slow to penetrate the snowpack down to the soil. As a result, you can get really cold air temperatures without much soil freezing.”
But remove the insulating snowpack, and the soil and tree roots freeze much more deeply.
“Historically, soil frost [got] to be a few centimeters in depth, but without the snowpack, it got down to over 30 centimeters,” Reinmann said.
At the end of the experiment, Reinmann collected cores from the trees. He found that tree growth declined by 40 percent after two years, and growth remained suppressed for the rest of the five-year study period. “That was a far larger decline than we expected,” he said. “Also surprising was that even a year after the experiment ended, tree growth didn’t rebound.”
The damage that the freezing temperatures inflicted triggered a cascade of responses: a reduced capacity of the trees to take up water and nutrients, shorter branch growth, and a decrease in soil insect diversity and abundance. “Whatever resources the trees may have allocated to growth, some of it had to instead be allocated to regrowing [the] root system,” Reinmann said.
The implications of these results could be significant. Reinmann concluded that “Left unabated, changes in climate could have a detrimental impact on the forests of the region and the livelihoods of the people who rely on them for recreation and industries such as tourism, skiing, snowmobiling, timber, and maple syrup production.”