Warming prevents tree leaves from cooling down.
An international group of scientists led by specialists from the State University Oregon stated that the leaves in the crowns of forests cannot independently cool below the temperature of the air that surrounds them. According to researchers, global warming may interfere with the ability of trees to absorb carbon dioxide from the atmosphere, EurekAlert reports. The research is also important for building an understanding of how plants respond to climate change.
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According to the lead author of the study, Chris Still, numerous studies show that forests are approaching their limit of oxygen absorption.
“The hypothesis, known as limited leaf homeothermy, states that due to a combination of functional traits and physiological responses, leaves can maintain their daytime temperatures close to optimal for photosynthesis and below values harmful to them. In particular, the leaves must be cooled below the air temperature at higher temperatures, which usually exceed 25 or 30 degrees Celsius. This theory also predicts that the effects of climate warming on forests will be partially mitigated by the response of leaves to cooling,” said Steele.
The scientist and his colleagues used thermal imaging images of forests in North and Central America. , which allowed them to monitor the temperature of the leaves. It turned out that the leaves do not always cool below the temperature of the surrounding air and do not always remain in a certain temperature range.
According to the researchers, the leaves of the canopy warm up faster than the air. For most of the day, it remains warmer than the surrounding air, cooling only in the middle or at the end of the day. Future climate warming is likely to lead to even greater increases in leaf temperature, which will affect the carbon cycle in forests and may put them at risk of dying.
Leaf temperature in different zones is affected by its size, as well as the structure of the crown and its dependence on climate. Large leaves are found mainly in warm and humid climates, and plants that grow in hot climates most often have small leaves with high reflectivity.
In most of the warm, humid tropics, leaf temperatures are already approaching or exceeding the threshold the value for positive net photosynthesis is the rate of carbon fixation minus the rate of loss of carbon dioxide during the “breathing” of plants.
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According to the researchers, further climate warming will lead to even greater increases in leaf temperatures, leading to reduced carbon sequestration and even more warming.
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