Minnesota forests could be harmed by climate change

A new UMN study found that a warmer climate would inhibit photosynthesis in trees.

Sunny Lim

A recent research study examining climate change in Minnesota found that rising global temperatures could harm forest growth in the state. 

The October study reveals soil moisture levels affect photosynthesis in trees — something that was previously unknown to scientists. It is part of a larger University of Minnesota research project called B4WARMED, which has been studying how Minnesota tree species will be impacted by climate change since 2008. 

“A decrease in photosynthesis could be a really bad thing because if you don’t have plants that are taking carbon dioxide in from the atmosphere, your atmospheric concentrations are just [going to] keep on growing and the planet is [going to] keep on getting warmer,” said Sam Reed, a University graduate student studying forest ecology.

The experiment began because researchers wanted to learn how plant cells’ physiological growth and survival will be affected by climate change, said Peter Reich, a professor in the Department of Forest Resources and lead author of the paper. 

“As scientists, we’re concerned about what’s happening in Minnesota and around the rest of the world, and it’s very hard to know how a changing climate will influence the forest without doing an experiment,” Reich said. “It’s very hard to use existing forests to explain what’s happening as the climate changes.” 

Along with Minnesota, the results of the experiment can be applied throughout cool and wet regions across the world, such as Canada, Northern Europe, Northern China and Russia, Reich said.

“Our study is showing that the associated changes in soil moisture will offset much or all of any of the benefits that you would get from warmer conditions in cool places,” he said.

Young trees from 11 different species and two forests in northern Minnesota were used as the experiment subjects. Trees between the ages of three and five years old were heated simultaneously from above ground with infrared heaters and below ground with resistance heating cables, Reich said. In total, the researchers increased the temperature of the test plots by 3.4 degrees Celsius, a projected possible temperature increase in Minnesota by 2100, said Artur Stefanski, a University researcher and co-author of the study. 

Although similar studies have been conducted by different groups, this experiment was conducted in forests and did not use chambers or greenhouses throughout the process.

“Obviously, there are advantages and disadvantages of each method,” Stefanski said. “However, we can call this study closer to natural conditions because there are no walls and no roof.”

Reich hopes the 10-year-old study will continue to produce useful results and help researchers learn more about climate change. 

“Long-term experiments like this are very rare, so we want to keep it going as long as possible to learn as much as we can about long-term changes,” Reich said. “We just finished our tenth year of treatments. If we can get it to 12 or 15 years, that would be great.”