A new scientific study released by a team at the University of New
Hamp****re shows that forests may influence the Earth's climate in
im****tant ways that have not previously been recognized.
When sunlight reaches the Earth's surface it can either be absorbed
and converted to heat or reflected back to outer space, where it
doesn't influence the Earth's temperature.
Scott Ollinger, a professor at the UNH Institute for the Study of
Earth, Oceans, and Space and the department of Natural Resources and
the Environment, and colleagues have discovered that, of the total
amount of sunlight that falls on forests, the fraction that gets
reflected back to space is directly related to levels of nitrogen in
their foliage.
While scientists have long known that nitrogen-rich foliage is more
efficient at pulling carbon dioxide out of the atmosphere, this new
discovery suggests that nitrogen plays an im****tant additional role in
the Earth's climate system that has never before been considered.
Specifically, trees with high levels of foliar nitrogen have a two-
fold effect on climate by simultaneously absorbing more CO2 and
reflecting more solar radiation than their low-nitrogen counterparts.
Ollinger and UNH colleagues Andrew Richardson, Mary Martin, Dave
Hollinger, Steve Frolking, and others, stumbled upon the discovery
while ****ing over six years worth of data they collected from research
sites across North America.
The study involved a novel combination of NASA satellite- and aircraft-
based instruments, along with meteorological towers from the AmeriFlux
network and leaf-level measurements to analyze various aspects of
forest canopies. When Ollinger noticed that the overall reflectivity
of forest canopies (also known as albedo) rose and fell in conjunction
with leaf nitrogen, he had a eureka moment.
"Bits and pieces of evidence for this have been around for years but
nobody put them together before because it's a question we hadn't even
thought to ask," Ollinger says. "Scientists have long been aware of
the im****tance of albedo, but no one suspected that the albedo of
forests might be influenced by nitrogen. And because most of the
effect is in the infra-red region of the sun's spectrum, beyond that
which human eyes can detect, the pattern isn't immediately obvious."
The newly discovered link between foliar nitrogen and canopy albedo
adds a new twist to the understanding of the climate system and the
underlying nature of ecosystem-climate interactions.
Changes in climate, air pollution, land use, and species composition
can all influence nitrogen levels in foliage, and all of these may be
part of a climate feedback mechanism that climate models have not yet
examined.
Future research planned by the team will involve examining the
underlying causes for why the relation****p exists and working with
climate modelers to determine how the nitrogen-albedo mechanism will
influence predictions of climate change.
On YouTube Now
Restoration forest project in northern Thailand
The Earth Charter Foundation is planting thousands of Magnolia X Alba
trees in a deforested mountain valley in northern Thailand.
www.youtube.com/watch?v=bN00Tijj_-0
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