A spot of old oaks in the UK is helping scientists to predict how the world’s forests will respond to higher levels of carbon dioxide.
Hidden in a quiet rural road in the West Midlands region of the United Kingdom One of the most studied forest fragments in the world.
This forest fragment, populated mainly by English oaks (Quercus Robur) com 180 years oldis in the center of a Great World Project designed to understand how the world’s forests will deal with the increase in carbon dioxide levels in the atmosphere.
This is a crucial question.
Globally, the Forests absorb about 7.6 billion tons of CO2 per yearonce the emissions from forest fires, deforestation and other disturbances are accounted for. The temperate forestslike those of the United Kingdom, They are responsible for almost half of this absorption.
But can we count on this carbon sink as pollution increases?
According to, in 2050atmospheric CO2 concentrations will be 40% higher than current levels if current trends remain. Many of the current trees will still be standing. How will they react?
Na Staffordshire Forestscientists have been submitting mature oak groups to a simulated future atmosphere. Since 2017, they have been pumping CO2 around these trees, raising local concentrations to 570 ppm.
Rob MacKenziefrom the University of Birmingham, in the United Kingdom, which generates the site, has been carefully observe the reaction of the trees.
Basic biology tells us that, with higher levels of CO2, the photosynthesis rate increases. In other words, trees and plants will respond to more CO2 in the atmosphere, extracting more of this gas.
As in young trees confirm This theory. But until recently, little was known about the reaction of the most mature trees.
“The way a young plant in a greenhouse or agricultural field responds for a short time is well known,” says Mackenzie. “But the way older plantwhich is on your soil there is 180 yearswill respond to a similar stimulus is completely unknown.”
A Answer is fundamental To ensure that climatic models correctly play the role of forests in the absorption of CO2 in the future. If the photosynthesis rate changes and the trees absorb more carbon, the overall carbon absorption rate of temperate forests will increase.
On the other hand, if the carbon absorption rate of the trees does not change, the role of forests as a climate solution will be smaller than thought. “We will influence the accuracy of the land system models in terms of their treatment of terrestrial carbon sink“Says Mackenzie.
Os Results so far are promising. After seven years in high CO2 conditions, mature oaks increased their photosynthesis rate and are producing about 11% more wood per yearcompared to neighboring trees in current atmospheric conditions.
“We are satisfied with the results because do not show a forest that will fall, ecologically speakingunder this type of stress. It seems that there is some adaptation capacity“Says Mackenzie. “It can be given, even when we enter an atmosphere with a high CO2 content, the terrestrial carbon sink keep its current role of bending the curve slightly [do CO2 atmosférico]”.
However, one in a mature eucalyptus forest in Australia, which also began in 2017, found no connection between the high atmospheric CO2 and the extra growth of the trees. Why is this British forest different?
The answer lies in Amazement of nitrogen and phosphorusessential nutrients that allow trees to use excess CO2.
In Australia, the forest was limited by the lack of nutrients, but the Staffordshire site has enough, in part, for the use of fertilizers in neighboring agricultural lands. “All in the results we have so far obtained is due to the fact that the forest has sufficient whip to use or carbon“Says Mackenzie.
There is also evidence that mature oaks are using new strategies to ensure their nitrogen supplies.
The team found that they are developing new root networks at a rapid pace to extract new ground nitrogen reserves and keep their reserves releasing less nitrogen through their roots and leaves. “These strategies allowed this forest to present no sign of nitrogen limitation,” he says Sami ullahalso from the University of Birmingham.
For Mackenzie, this represents a remarkable change in the activity of middle-aged trees. “They had 180 years to explore the ground,” he says. “It is possible to think that the soil is completely mapped from the perspective of the plant. But it turns out that there are still things they can do if the feature changes. ”
There are other changes ongoing in the forest. Trees in high CO2 conditions have more bitter chemicals in their leaveswhat the investigation team suspects that it may be a sign that they are investing more in their resistance to pests and diseases.
There are also signs that these trees may be recovering faster from short periods of stress thermalresuming photosynthetic activity before control trees.
But the maintenance of this accelerated rhythm of activity depends on the abundance of nitrogen.
In Western Europe, the liberal use of agricultural fertilizers left the Overloaded azoto soils. Trees under high CO2 are now absorbing this excess, but this may not last forever.
In previous high CO2 experiences performed on younger trees, nitrogen supplies eventually decreased, leading to a drop in photosynthesis rate. “If the trees are using more nitrogen, they will eventually exhaust the nitrogen from the ground,” he says Anna Gardnerfrom the University of Birmingham. “It’s a positive story for us so far, but in the long run we’re not sure.”
A Staffordshire experience will take place by 2030when investigators expect to have unveiled If nitrogen limitation is a serious threat for temperate forests.
Another experience with high CO2 is being built in the Amazon Florestato test the reaction of tropical forests.
However, the change in CO2 concentrations cannot tell us much. Although these tests can simulate future atmospheric CO2 levels, they cannot simulate the future climate.
In any case, the Madeira is also just a temporary carbon reserve. Even though trees survive the growing threats of droughts, heat waves, floods, pests and disease, they will eventually die. When wood rots, the stored carbon is release again to the atmosphere.
It would therefore be foolish to trust forests too much as climate saving, Mackenzie says, even if his increased photosynthesis rate is sustained. “It is just help; It is not a solution“He concludes.
Teresa Oliveira Campos, Zap //
