A new study led by Oregon State University has found that changing temperatures in forests due to climate change will damage the ability of trees to cool their leaves and remove carbon dioxide from the atmosphere in warmer climates.
The new findings challenge an earlier theory that forest leaves can maintain their temperature within an optimal range for photosynthesis, which is the process by which green plants produce their food from sunlight and carbon dioxide. carbon
Advances in the response of plants to climate change
Existing research suggests that many of the world’s forests are approaching their thermal limit for carbon sequestration.
Building on this, new research published in the Proceedings of the National Academy of Sciences used thermal imaging to study forest leaf temperatures at sites in North and Central America, including the Panamanian rainforest and the Line of ‘high elevation trees in Colorado.
Thermal cameras were mounted on towers equipped with technology to measure carbon, water and energy flows between forests and the atmosphere.
“Using continuous, high-frequency thermal imaging to monitor forest cover really changes what we can learn about how forests cope with the stress of rising temperatures,” said Andrew Richardson, professor at Northern Arizona University and co-author of the study. .
“Before thermal cameras, if you wanted to measure canopy temperature, you had to tape thermocouples to the leaves and wait for the wind to blow them off. But these cameras allow us to measure the change 24 hours a day, seven days a week, through many seasons and years.”
The results of these tests found that forest leaves do not consistently cool below daytime air temperatures or stay within a narrow temperature range. This contradicts the theory of leaf homeothermy, which was limited in its research.
Chris Still of the OSU College of Forestry said, “A hypothesis known as limited leaf homeothermy argues that through a combination of functional traits and physiological responses, leaves can maintain their daytime temperatures close to their optimum temperature for photosynthesis and below that which is harmful to photosynthesis. them.”
“Specifically, leaves must be cooled below air temperature to higher temperatures, typically above 25 or 30 degrees Celsius. This theory also implies that the impact of climate warming on forests will be mitigated partly by the cooling response of the leaves.”
However, the new research found that the forest warms faster than the air during most of the day, only cooling in the afternoon.
What do the findings mean for the future of forests?
In warmer climates, those leaving forests are already approaching or even exceeding thresholds for processing carbon dioxide.
As future climate warming is likely to lead to even greater forest temperatures, the process of leaf carbon cycling would be adversely affected. Scientists say this could improve moral hazard in forests.
“If leaves are generally warmer than the surrounding air, as our findings suggest, trees may be approaching critical temperature stress thresholds faster than we expect,” Richardson said.
“Our results have major implications for underestimating how plants acclimate to warming, and suggest a limited ability of canopy leaves to regulate their temperature,” Still added. “Our data and analysis suggest that climate warming will result in even higher canopy leaf temperatures, likely leading to reduced carbon assimilation capacity and ultimately heat damage.”