On a cool day in late May, researcher Pamela Templer hikes through New Hampshire's White Mountains with ease, dodging an odd low-hanging branch as leaves and sticks crunch underfoot.
Although she's in the middle of a national forest, Templer's destination looks decidedly unnatural.
A cabin full of controllers and wiring sits plopped amid the trees. Newly erected power lines march up to the forest's edge. And a sign with a lightning-bolt graphic warning reads "Research Area: Do Not Walk Beyond This Sign."
This forest, Templer explains, is wired.
"Last summer, we buried almost 4 kilometers [2.5 miles] of heating cables in the ground," she said.
What Templer hopes to do with those cables, some shovels and a five-year experiment at the Hubbard Brook Experimental Forest is better understand the effect climate change might have on New England forests.
Simulating warming through 4-inch cables
While the effects of warming on forests have been studied before, Templer's experiment adds a unique and important twist.
Her warming cables, buried 4 inches deep, will simulate what will happen to the forests in summer as the climate warms. Those cables snake through four of Templer's six plots, which are about 40 by 46 feet in size, each with three red maples in their center.
The cables will heat the soil by 5 degrees Celsius during the growing season.
The maples, which are going to be measured for root growth and other factors, such as how well they take up nutrients from the soil, might actually like this warming, Templer explained. Other experiments that have warmed the soil have found that trees can grow faster and may be able to absorb more nutrients.
But those experiments fall short in their representation of the New England winter as the climate changes.
That's because they heat the ground year-round. In winter, at least for the next 100 to 200 years, New England soils will actually get colder as snowpack shrinks.
This is already happening. Records from Hubbard Brook, kept since the 1950s, have shown that snowpack in the forest has steadily decreased, and the snow that does fall stays on the ground for less time.
"It's somewhat counterintuitive, but snow actually acts like a blanket," Templer explained. "And so if you have a sufficient snowpack on the ground, all the organisms that live under that snowpack are snuggly warm. It's like being inside of an igloo."
That's why Templer's experiment adds a key element in the winter. When snow does fall, she is going to shovel it off two of the four plots that are getting added summer warming. The other two plots are a control.
"We are going to take away snow to induce soil freezing," she said.
Scientists probe warming and nitrogen link
Templer's prior research on how New England's forests respond to less winter snow has shown that without the protective snow blanket, soils freeze, causing damage to soil organisms and tree roots.
Scientists first noticed the damage frozen soils could cause to trees over two decades ago, when something strange happened at Hubbard Brook, which is continuously monitored because of its status as a research forest.
In the summer of 1990, scientists in the forest saw higher levels of nitrogen in the streams there, said Peter Groffman, an ecologist at the Cary Institute of Ecosystem Studies in New York, who has worked with Templer on experiments at the forest.
Other researchers in Northeastern forests noticed this happening, as well.
Normally, plant roots in the forest will soak up nitrogen as they come out of dormancy in spring and use it to grow. The scientists searched for a change that may have kept this from happening, so that more nitrogen flowed into the creeks.