On the Northern Front of Climate Change
In the Arctic, the trees are tiny and conservative. They have to be. They grow only fractions of an inch a year, saving energy to make it through long, dark winters. Yet these small trees could play a huge role as the climate changes.
“If the trees move farther north, they will have a big impact on the energy balance of the Earth,” said Jan Eitel, assistant professor in the University of Idaho’s College of Natural Resources. “Right now, if you look at the tundra in the winter, it is white. If more trees grow there, they will make everything darker and that effects the Earth’s energy balance.”
That’s not all. According to Eitel, the more trees grow in the Arctic the more they will influence carbon and water cycling as they replace the smaller grasses and shrubs now on the tundra.
To find out how these important trees are faring, Eitel is leading a four-year, $1.2 million research project as part of NASA’s ABoVE (Arctic-Boreal Vulnerability Experiment) program to study tree health in the forest-tundra ecotone, the transition zone where trees of the boreal forest meet the flat, treeless Arctic plains.
“What’s ironic is that some of the least understood regions of the world are some of the most important to understanding how the Earth works,” Lee Vierling, Professor, Head of Department of Natural Resources and Society
The forest-tundra ecotone is not limited to Alaska — it is circumpolar, spanning 8,000 miles around the globe. It is one of the world’s most important transition zones but yet scientists know little about how it functions because it is so vast and hard to access.
“What’s ironic is that some of the least understood regions of the world are some of the most important to understanding how the Earth works,” said U of I Professor Lee Vierling, who is collaborating with Eitel on the project.
Just to get to their research sites, the scientists must drive hundreds of miles north into Alaska on a lonely road built by pipeline workers decades ago. For several weeks in the spring, summer and fall, they live above the Arctic tundra at the remote Toolik Field Station. Each day, they drive back south into the Brooks Mountain Range deep in the state’s northern interior until they get to the place where a few trees manage to break through the nearly frozen ground.
“It’s the most beautiful commute you could ever imagine,” Eitel said.
“So long as your truck doesn’t break down,” Vierling added.
Addressing problems of access, scale and — bunnies
To tackle the challenges of studying this region, the researchers use both technology and collaboration. The U of I faculty, Eitel and Vierling, along with doctoral student Andy Maguire, bring their expertise in using lidar imagery and pair that with the tree physiology and ecology expertise of Columbia University researchers Professor Kevin Griffin and Associate Research Professor Natalie Boelman.
The team has set up a variety of instrumentation at their Alaskan sites, from sensors that can measure the daily submillimeter ring growth of individual trees to terrestrial lidar. They also use aerial lidar data collected from planes and satellite imagery that show the reflected light from trees on much larger scales that can help track growth rates.
Lidar, which sends out laser pulses to create a 3-D map, is particularly good at characterizing structure, according to Maguire. He is leading much of the data analysis on the project from sites in Alaska and Canada.
“You can tell something about a plant by how much light is hitting the leaf, and then based on how much light is coming off it, you can get a much better sense of what photochemical growth processes are happening inside that leaf,” he said.
The lidar and satellite data are then compared with the ground-based measurements of tree health.
“What we look for are ways to connect observations in the field at a very limited scale that we can access, up to broader areas that we can see with satellites and airplanes,” Vierling said.
If the measurements indicate the trees are doing well, the northern tree line will likely advance in the future. If they are struggling, it might retreat.
The researchers overcome many obstacles to get the data they need. In addition to the difficult travel, the weather can swing from hot and sunny to cold and snowy at any point. The mosquitoes are ferocious in the summer, and in the winter, so are the bunnies.
A sudden population surge in snowshoe hares has endangered both trees and equipment. The hares often strip the bark off of trees, and – in their voracious search for sustenance – chew on the cables of tree health monitors and lidar equipment. On the past few trips, the scientists had to set up chicken wire to protect their instruments and even consider whether the hares may play a role in regulating treeline.
The project team remains optimistic that gathering data in this difficult environment will pay off as they start to analyze what they have found.
“We continue to be surprised with how these seemingly remote locations are in fact telling a larger story about how people and the environment are interconnected,” Vierling said.
“Basically, we’ve done lot of important ground work, and in the next few years, I expect a lot of interesting findings will come out of it,” Eitel said.
Article by Sara Zaske, College of Natural Resources
Published August 2018