Pop Open a Nice Cold Forest
Release Date: 04-15-2009
How much snow in these woods? Nick Rustigian '09, Hedda Peterson '10, and Sean Donovan '12 were among nine students who traveled to New Hampshire's Hubbard Brook Research Forest to help UVM geographer Beverley Wemple dig into this question. (Photo: Joshua Brown)
It's a dappled April afternoon on a hardwood slope in the White Mountains of central New Hampshire. Four University of Vermont undergraduates huff uphill on aluminum snowshoes, deep in the US Forest Service's Hubbard Brook Experimental Forest. Snow lies in granular strips and blobs, covering most of the leafy floor like a cake frosting project gone bad. The students are silent while the wind and fickle sun argue between March and May.
They head into a shaded patch of beech where snow remains deep. Each tree sticks out of a melt-hole made by its own trunk as it absorbs and re-radiates the spring sunshine.
The snow is a potent mix of rotten and slippery. Sometimes, despite the snowshoes, the students sink up to their thighs. But, in several clear-cuts nearby, brown grasses stand dry, like a droughty summer meadow. Meltwater trickles down gullies every few feet. Last fall's beech leaves still cling preposterously to branches, but winter is losing. Soon the snow will be gone from here — into the ground, rivers, air and the Atlantic Ocean seventy-two miles to the east.
The students take their bearings off a tree marked with surveyor's tape and then stretch a yellow tape measure into the forest. Along this transect, Nick Rustigian '09 plunges a five-foot-long snow-collecting tube downward, turning it slightly to engage the sawteeth along the bottom edge.
He peers at the ruler that runs along the length of the tube. "42 inches," he says, and then eases the nearly full tube out of the snow. He gingerly places it horizontally on hooks attached to a small electronic weighing scale that Hedda Peterson, a sophomore from Worcester, Vt., holds in front of her. "One point nine nine kilograms," he says. Eden Furtak-Cole '09 records the data on a clipboard. They move down the line ten meters to collect the next sample.
They're tired. Their boots and legs are sodden. They've been working all day for Beverley Wemple, professor of geography, who has employed them through a National Science Foundation grant that supports undergraduates participating in research. This is the last data collection point of the afternoon. Rustigian admits to being "wiped out." Once they're done here, they've got to walk several miles out because the off-road "mule" they were borrowing from the Forest Service threw off one of its tank-like treads.
"It's definitely hard work," says Peterson. But some inner sun still shines. Asked why she is doing this, she pauses. "It's meaningful to be part of scholarly research," she says, considering her own words.
The meaning of melt
And Wemple's scholarly research is meaningful to more than hydrologists. Among other things, she studies snow. More specifically, she is interested in how forests in the eastern United States affect melt rates and distribution of snow.
"There is a real need for this information beyond science," she says, "anyone running dams or predicting water supplies for cities needs to know about runoff," she says. And that means knowing about how much water is held in the snow pack and where it's located.
"The coniferous forests of the West have been well studied and we know that the trees have a major impact on the snow pack there," she says.
"But in the East, they haven't been studied much. Many people say that forests in the East don't have a big effect or intercept much snow because they lose their leaves," she says, "I'm questioning that."
She has reason to. For the last eight years she has studied two adjacent watersheds on Mount Mansfield in Vermont, one intact, the other developed. "When you cut the forest, you get a lot more run-off," she says. "But how much more and why?" Her data show run-off from the developed watershed to be higher than expected — or than stormwater planning models had predicted.
And more development and forest clearing seems likely in Vermont and the rest of New England. "The reason this deserves attention is because we are going to go back into our forests big time," she says.
The reforesting of the northeastern U.S. is a conservation success story. In the 1850s, Vermont was about 80 percent cleared, 20 percent forest; now the statistic is nearly reversed. But that story may be coming to an end. In the approaching era of scarce oil, biomass energy production, and expanding exurban developments, Wemple believes that "in the next few decades we're probably going to starting harvesting our forests again — hard."
"We need to understand all the implications of this not just for habitat and timber supply, but for water resources as well," she says. For one thing, forests process about two-thirds of the freshwater supply in the United States, according to the National Research Council. It's not much of a stretch to say you drink the forest.
"And if we end up with a warmer climate and less snowfall that's going to be important," magnifying the hydrological effects of lost forest cover, she says. "Snow melts slowly and recharges soil water."
"If you have less snow — for whatever set of reasons — then water moves through the system more quickly and there is less recharge," she says. It's not too surprising that managers from New York City's watershed contacted Wemple to learn better techniques to measure the amount of water held in snow.
"Unfortunately no one has a really good handle on that yet," she says.
Which is why she has started a study here at Hubbard Brook. "This year, we're asking: can we detect a significant difference between forests and clearings?" Next year, she and two faculty colleagues in engineering and computer science, Jeff Frolik and Christian Skalka, plan to test wireless sensors here to see if they can do this same snow measuring work remotely.
But, for now, "the students are worker bees," Wemple says, "there is a lot to be learned — and there's a lot of grunt work. I mean, that's science!"