Study: Climate change could hamper forests’ ability to draw carbon from the atmosphere


A new study reports that the ability of forests to withdraw carbon dioxide from the atmosphere will be affected as the planet warms due to climate change, and scientists explain the process of photosynthesis in which leaves convert sunlight and carbon dioxide into oxygen and energy in the form of sugar, which occurs better. Between 59°F and 86°F (15°C and 30°C), canopy sheets are widely accepted to be able to maintain an ideal temperature for photosynthesis, even when the surrounding air is heated.

According to the “RT” website, researchers at Oregon State University found that leaves actually struggle to regulate their temperature when they get hot, and they predict that global warming could impair the leaves’ ability to stay cool and thus conduct photosynthesis, especially in warm climates.

Lead researcher Dr Chris Steele said: ‘Leaf temperature has long been recognized as important to plant function due to its impact on carbon metabolism and water and energy exchange.

“Photosynthesis is necessary for the survival of green plants and releases oxygen as a by-product, and the rate at which the plant absorbs carbon must exceed the rate of carbon dioxide lost during respiration in order to have a net positive photosynthesis,” Steele added.

It is believed that the leaves have a variety of mechanisms that enable them to keep cool even with a high ambient air temperature, in what is known as the “household leaf heat.” It includes changing the angle of the leaf in relation to the sun, and sacrificing some water as “sweat” that condenses from its surface and lowers its temperature.

The ability of the leaves to do this is necessary to maintain an optimum temperature for photosynthesis, allowing the process to occur faster than respiration, and the mechanisms also reduce the risk of heat stress and leaf necrosis, or tissue death due to limited water flow.

Dr Steele said: ‘The hypothesis known as limited household heat for leaves says that through a combination of functional traits and physiological responses, leaves can maintain a daytime temperature close to the best temperature for photosynthesis and lower than it is detrimental to it. Leaves cool below air temperature at higher temperatures, usually above 25 or 30 degrees Celsius.”

This theory also suggests that the impact of climate warming on forests will be partially mitigated by the “cooling response” of the leaves.

But the study, published today in the Proceedings of the National Academy of Sciences, suggests that leaves in forest canopies are unable to do this.

The researchers used thermal imaging to examine the temperature of canopy leaves at several well-groomed locations in North America and Central America over several seasons, including the Panama rainforests and the Colorado highland tree.

Thermal cameras are installed on towers equipped with systems that measure carbon, water and energy “flows” – the exchanges between the forest and the atmosphere – as well as a range of environmental variables.

He found that canopy leaves did not continuously cool themselves below daytime air temperatures or stay within a narrow temperature range, and canopy leaves warmed faster than air, contrary to what the leaf finite heat theory predicted.

Their temperature actually remained higher than the surroundings for most of the day, only to cool below mid-afternoon air.

According to the researchers, since future climate warming is likely to lead to higher leaf canopy temperatures, the observed inability to self-regulate could lead to serious problems for forest trees, and heat can cause leaves to exceed the thermal limit, as net negative photosynthesis begins. The risk of forest death increases.

“If leaves are generally warmer than the ambient air, as our findings suggest, trees may approach critical thresholds for temperature pressure faster than we expect,” said study co-author Andrew Richardson, a professor at Northern Arizona University.

Scientists say the temperature of the leaves is also affected by their size, which varies according to the climate and habitat, such as latitude or the structure of the canopy.

According to experts, plants that grow in hot and dry areas are usually smaller and have a greater ability to reflect sunlight, which allows them to shed more heat, however, those that grow in warm and humid climates have larger leaves, and therefore can actually approach or Exceeds net positive photosynthesis thresholds.

“Our results still have significant implications for understanding how plants adapt to warming, and they indicate a limited ability of canopy leaves to regulate their own temperature, and our data and analyzes indicate that a warming climate will lead to higher temperatures for canopy leaves, potentially resulting in To reduce the ability to absorb carbon and eventually heat damage.

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