Taking Measure of a Remote Slice of Alaskan Forest

Kate Legner points out the next tree in the survey site as other crew members measure key information about the vegetation in a 53-foot diamter plot.

In a birch forest in interior Alaska’s Tanana Valley, there’s a stake with pink plastic tape attached. More than three decades ago, a plane flew over it to take stereoscopic pictures of the surrounding plot, and scientists trekked out to survey the trees and vegetation. Now, scientists are re-flying and re-surveying the site, using advanced airborne instruments and satellite images to track changes in interior Alaska.

“This is going to be 10.3,” called out Sean Cahoon, a scientist with the University of Alaska, Anchorage. He was standing at the end of a tape measure radiating out from the stake, using another tape measure to check the diameter of the base of a birch tree.

Kate Legner, with the University of Washington in Seattle, recorded the number as well as the diameter at breast height, the distance from the stake, and the azimuth (angle from due north) of the tree’s location.

“That’s all you need to recreate this whole area,” Legner said. The area in question is a circle with a 53-foot radius out from the stake. Mostly birch, with a few aspen and white spruce trees, just sparse enough to let some sun filter through to shrubs, seedlings, moss and lichens thick on the ground.