Climate change is causing trees to take up less carbon dioxide despite a longer growing season, according to research conducted by Indiana University researchers that was published this week.
Warmer average temperatures are causing trees to keep their leaves longer, but they actually are growing less because of more drought-like conditions.
IU doctoral student Eddie Brzostek was the main author on a paper published this week in the journal Global Change Biology. He and a group of researchers used data from the Morgan-Monroe State Forest in Indiana and the U.S. Forest Service to estimate the impacts climate change would have on dozens of species.
“The Morgan Monroe State Forest is dominated mostly by maple and tulip poplar and these tree species showed really strong declines with drought so their growth declined rapidly, whereby oaks tended to be more resilient,” he says.
So if most of the trees in the state forest aren’t growing as much because of drought, they aren’t taking in as much carbon dioxide. The report predicts the decline would be equal to between one and three days of global carbon emissions each year.
The Department of Natural Resources does not take a position on climate change, but State Forester John Siefert says the drier conditions could actually help oaks beat out the smaller trees.
“You’re going to see those oaks come through that canopy as those as we call early successional and mesic tree species will succumb to the drought,” he says.
Brzostek says that does not seem likely to happen because historically additional factors besides climate, including natural fires, helped kill off other trees and allowed oaks to establish dominance in the forest.
Brzostek says so far the maples and tulip poplars are still growing, they just aren’t growing as quickly and are therefore taking in less carbon dioxide.
The DNR has been exploring multiple ways to improve oak regeneration, but Seifert says many of the man-made techniques are cost prohibitive.
A companion study, also published this week in Global Change Biology, identifies a new way to detect the impact water shortages have on forest growth.
Researchers found that information gathered from grasslands and agricultural fields in and around the majority of forests is a better indicator of water shortage impacts than previous methods.
Those included using national satellite and site data from the Morgan Monroe State Forest and the Missouri Baskett Wildlife Research area in the Ozarks to determine how green or brown forest canopies were.