According to a new study, trees struggle to sequester CO2 in drier and warmer climates. This means that they may no longer help in solving and offsetting humans' carbon footprint as global warming continues.
Trees Struggle To Breathe
Max Lloyd, the study's lead author and an assistant research professor of geosciences at Penn State University, explains that they discovered that trees in drier and warmer climates are essentially coughing rather than breathing. Trees in these climates have been releasing CO2 back into the atmosphere significantly more than trees in wetter and cooler conditions.
Trees remove atmospheric carbon dioxide through photosynthesis to yield new growth. However, when these trees are under stressful conditions, they release carbon dioxide into the atmosphere, a process known as photorespiration.
With an analysis of the tree issue's global dataset, the researchers showed that photorespiration rates could double in warmer climates, especially when water levels are limited. The researchers observed that in subtropical climates, the response's threshold starts being crossed when the average daytime temperatures go beyond around 68 degrees Fahrenheit and get worse as temperatures go even higher.
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Plants and Climate Change
The "Isotopic clumping in wood as a proxy for photorespiration in trees" study complicates the belief that plants could play a role in drawing down or using atmospheric carbon. It also offers insight into how plants may adapt to climate change.
The researchers note that their findings show that, as global warming continues, plants could be less able to draw carbon dioxide from the atmosphere and assimilate it, which is necessary for the planet to cool down.
Lloyd explains that this crucial cycle has been knocked off balance. As the most significant drawdown of the atmospheric atmosphere is organisms that photosynthesize, little changes could yield grave impacts.
The US Department of Energy notes that plants absorb around 25% of the carbon dioxide that human activities emit yearly. However, this figure could decrease significantly as climate change persists if water scarcity worsens.
The researchers also found that variations in the abundance of an isotope of a wood part known as methoxyl groups are tracers for tree photorespiration. They looked into methoxyl levels of the isotope in samples of wood taken from roughly thirty specimens of trees from different conditions and climates worldwide. They did not observe photorespiration trends. The specimens were from an archive of the University of California, with hundreds of samples taken from the 1930s and 40s.
Since the team has now validated a method for photorespiration observation through wood, this method may offer a tool for predicting how trees could breathe in the future and how they fared in climates in the past.
The researchers will now go on to unearth the rates of photorespiration in the past, as far back as tens of millions of years. With this, their hypothesis, which regards how plant photorespiration could affect climate over geologic time, can be explicitly put to the test.
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