Contrary to conventional belief, as the climate warms and growing seasons
lengthen subalpine forests are likely to soak up less carbon dioxide, according to a
new University of Colorado at Boulder study. As a result, more of the greenhouse
gas will be left to concentrate in the atmosphere.
"Our findings contradict studies of other ecosystems that conclude longer growing
seasons actually increase plant carbon uptake," said Jia Hu, who conducted the
research as a graduate student in CU-Boulder's ecology and evolutionary biology
department in conjunction with the university's Cooperative Institute for Research in
Environmental Sciences, or CIRES.
|A surprising new
CU-Boulder study indicates subalpine forests in the West will soak up less carbon
dioxide as the climate warms and the growing seasons lengthen. Image courtesy
Steve Miller, CIRES. |
The study will be published in the February edition of the journal Global Change
Biology. Working with ecology and evolutionary biology professor and CIRES
Fellow Russell Monson, Hu found that while smaller spring snowpack tended to
advance the onset of spring and extend the growing season, it also reduced the
amount of water available to forests later in the summer and fall. The water-
stressed trees were then less effective in converting CO2 into biomass. Summer
rains were unable to make up the difference, Hu said.
"Snow is much more effective than rain in delivering water to these forests," said
Monson. "If a warmer climate brings more rain, this won't offset the carbon uptake
potential being lost due to declining snowpacks."
Drier trees also are more susceptible to beetle infestations and wildfires, Monson
The researchers found that even as late in the season as September and October,
60 percent of the water in stems and needles collected from subalpine trees along
Colorado's Front Range could be traced back to spring snowmelt. They were able
to distinguish between spring snow and summer rain in plant matter by analyzing
slight variations in hydrogen and oxygen atoms in the water molecules.
The results suggest subalpine trees like lodgepole pine, subalpine fir and
Englemann spruce depend largely on snowmelt, not just at the beginning of the
summer, but throughout the growing season, according to the researchers.
"As snowmelt in these high-elevation forests is predicted to decline, the rate of
carbon uptake will likely follow suit," said Hu.
Subalpine forests currently make up an estimated 70 percent of the western United
States' carbon sink, or storage area. Their geographic range includes much of the
Rocky Mountains, Sierra Nevada and high-elevation areas of the Pacific Northwest.
Study co-authors included David Moore of King's College London and Sean Burns
of the National Center for Atmospheric Research and CU-Boulder.
CIRES is a joint institute of CU-Boulder and the National Oceanic and Atmospheric
Administration. For more information about CIRES visit cires.colorado.edu.
Contact: Jia Hu, 303-492-5796
Russell Monson, 303-492-6319
Morgan Heim, 303-492-6289
Bookmark or post this science news