Warming Climate May Hurt Trees' Carbon Uptake
According to a new report, a warming climate is diminishing the carbon absorption capacity of trees, leaving more greenhouse gas to compound in the atmosphere.
"Our findings contradict studies from other ecosystems that conclude longer growing seasons actually increase plant carbon uptake," said Jia Hu, who conducted research for the report at the University of Colorado's Ecology and Evolutionary Biology Department in conjunction with the university's Cooperative Institute for Research in Environmental Sciences (CIRES).
The study finds that reduced springtime snow packs extend the growing season, but they also reduce water supply available to trees later in the summer and fall. Those trees are then made less efficient in converting carbon into biomass and, because their water content is reduced, they are more susceptible to damage via beetle infestation and wildfires. The reduced-capacity trees also allow more carbon to remain in the air.
"Snow is much more effective than rain in delivering water to these forests," said CIRES Fellow Russell Monson. "If a warmer climate brings more rain, this won't offset the carbon uptake potential being lost due to declining snow packs," he said.
Subalpine forests currently make up an estimated 70 percent of the western United States' carbon sink. Their geographic range includes much of the Rocky Mountains, Sierra Nevada, and high-elevation Pacific Northwest.