Today across the Upper Midwest, the aging aspen and birch trees that dominate the forest canopy are starting to die of old age. The sun-hogging aspen and birch are gradually giving way to understory species---red maple, beech, white pine, red pine, and red oak---currently stuck in partial shade.
As the aspen and birch drop out, the increased sunlight should boost the growth rate among the pines, oaks and maples, leading to a more complex, multi-layered canopy. The FASET experiment is designed to speed up that transition, acting like a time machine that allows scientists to measure future carbon uptake now.
"We're simply accelerating the natural process of succession to allow the pine and the hemlock and the oak to come up and take their position in the canopy a little faster than they otherwise would, so that we can address the question, What will these future forests be like"" said Peter Curtis, an Ohio State University ecologist and the FASET principal investigator.
Aspen and birch will be killed in an 83-acre "treatment stand" using a technique called girdling. Instead of felling the trees with chainsaws, workers use the saws to inscribe two shallow, parallel cuts that encircle the tree trunk. Other workers follow with hammers and steel pry bars, stripping a band of bark from the trees.
Girdling trees kills them while preventing them from sprouting new shoots. Sugars produced in the leaves can't make it down to the roots, which slowly starve. But water, minerals and growth hormones called cytokinins continue to flow up to the canopy.
If the trees were simply cut down, cytokinins would accumulate in the roots and signal the tree to sprout new shoots. The end result, over time, would be even more aspens.
In the coming years, atmospheric carbon dioxide uptake in the treat
|Contact: Jim Erickson|
University of Michigan