Birch Trees To Edge Out Aspens In Warming World

[n2doc]

Science Daily — Birches will likely drive out many aspens in northern forests as mounting levels of carbon dioxide force the trees to compete more fiercely for soil nutrients in the coming decades, a University of Michigan researcher and his colleagues have concluded.

Carbon dioxide is emitted when fossil fuels are burned, and it's a heat-trapping gas blamed for global warming. But rising carbon dioxide levels also have a fertilizing effect on trees and other plants, making them grow faster than they normally would.

At a 38-acre experimental forest in northeastern Wisconsin, U-M microbial ecologist Donald Zak and his colleagues have been pumping extra carbon dioxide into the tree canopies since 1997 to simulate atmospheric conditions expected in the latter half of this century. The forest contains several thousand trembling aspen, paper birch and sugar maple trees.

Mixed aspen-and-birch stands bathed in extra carbon dioxide grow about 45 percent faster than their untreated neighbors. To sustain that speedy growth, the experimental trees had to find a way to extract more of the essential nutrient nitrogen from the soil.

It appears that the extra carbon dioxide (CO2) helps the trees do just that, by allowing them to grow more roots and "forage" more successfully for nitrogen, said Zak, a professor at the U-M School of Natural Resources and Environment and the Department of Ecology and Evolutionary Biology.

The birch trees seem better at nitrogen foraging than aspens, said Zak, one of the lead scientists at the federally funded experiment in Rhinelander, Wis. In mixed stands of aspen and birch subjected to elevated carbon dioxide levels, birch trees increased recent nitrogen acquisition by 68 percent, compared to a 19 percent increase among the aspens.
"The implication from that experiment is that it could alter the abundance of birch and aspen—in places like Michigan—by favoring birch," Zak said.

http://www.sciencedaily.com/releases/2007/09/070905151422.htm

[eppur_se_muova]

1. Where will the aspens turn now?

(On the plus side ... more birch beer.)

[Colorado Progressive]

2. Well, where I live birches would not survive the altitude, unless

the climate warms significantly. Lets face it, with global warming and a changing atmosphere we will lose a lot of species. Get used to it. I think aspens are one of the most beautiful trees on the planet, and I hope they can stick it out. They do grow like weeds, and I think/hope they will adapt.