Sure, accidentally heating the planet has been pretty easy. But try intentionally heating a plot of forest, and you get a whole other story.
In this week’s Nature, we take a brief look at a series of new experiments to test how warmer temperatures will change the composition of forests in different regions of the United States. Will forests begin to sprout above the tree line in the Colorado Rocky Mountains? Will oaks sweep northwards, deeper into the boreal forests of the northern United States and Canada?
Unfortunately, reliably and evenly heating a stand of grown trees to a set number of degrees above ambient temperature turns out to be pretty difficult to do. For now, these projects are limited to seedlings which will outgrow their heaters within a few years. Such studies are valuable in their own right – seedlings lack the extensive root networks that could help them survive a hot, dry summer, and are therefore a weak link in the chain of forest succession. Still, wouldn’t it be great if we could see the effects of climate change on the grown-ups, too?
Researchers are hoping that the next generation of large-scale experiments to address the impact of global warming on forests will include a heating component (see ‘Forestry carbon dioxide projects to close down’, subscription required, for more on this), but at the moment, it’s unclear what those experiments will look like. Bruce Kimball, a soil scientist at the US Department of Agriculture’s Arid-Land Agricultural Research Center in Maricopa, Arizona, has been using infrared heaters to study the impacts of warming on agriculture for years. He’s recently started trying to work out how many heaters it would take to heat a stand of trees in a 100 metre-diameter plot. Early calculations suggest he would need 199 heaters arranged in a honeycomb pattern to achieve even heating. “I’m quite confident that I could come up with a configuration to get the energy distributed satisfactorily,” he says. “Whether we could get the dollars it would take to do such an experiment is another matter.”
Others have been looking at ways to heat the air. “It’s a little bit different for the ecosystem to experience warmer air than to have to surfaces heated,” says Lara Kueppers, an ecologist at the University of California, Merced. “So people are brainstorming: how do you create what is essentially a giant hair dryer?” Look for the US Department of Energy to decide which prototypes it will fund towards the end of this fiscal year.