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Global warming will reduce the amount of carbon stored in forests, a new study warns.
Scientists say trees tend to "live fast and die young" in the world's warmer climate.
The research team, led by scientists at the University of Cambridge, said rising temperatures are boosting annual tree growth but reducing their lifespan.
The overall result, they say, is a reduction in the amount of carbon stored in forests as they return to the environment after death.
The carbon of plants and trees enters the carbon cycle when they die, eventually resulting in carbon dioxide – a greenhouse gas.
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Scientists at the University of Cambridge have found that as temperatures rise, trees grow faster – but they also tend to die earlier (stock)
Warm temperatures provide ideal growing conditions for trees that researchers say do not prepare the plant for adversity.
They say that the lack of "hardening" often leads to the death of trees when those grown in colder climates could survive.
The researchers said their findings had implications for the dynamics of the global carbon cycle and ultimately for the amount of CO2 in the atmosphere.
As the Earth's climate continues to warm up, they say tree growth will continue to accelerate, but the time trees store carbon – called "carbon residence time" – will decrease.
During photosynthesis, trees and other plants absorb carbon dioxide from the atmosphere and use it to build new cells.
The research team explained that long-lived trees, such as high-altitude pines and other conifers found in forests of northern latitudes, can store carbon for many centuries.
Prof. Ulf Büntgen, Department of Geography, University of Cambridge, said: "As the planet heats up, plants grow faster. It is therefore believed that planting more trees will remove more carbon from the atmosphere.
"But it's only half the story. The other half has not been taken into account: these fast-growing trees retain carbon for shorter periods. & # 39;
Professor Büntgen uses the information contained in dark circles to study past climatic conditions.
He explained that tree rings are as distinctive as fingerprints: the width, density and anatomy of each annual ring contain information on this year's climate.
By taking basic samples from live trees and dead tree samples from records, scientists are able to reconstruct the behavior of the Earth's climate system in the past and understand how ecosystems responded and responded. to temperature variations.
As the Earth's climate continues to warm up, they say tree growth will continue to accelerate, but the time trees store carbon – called "carbon residence time" – will decrease ( picture in stock)
For the present study, Professor Büntgen and colleagues from Germany, Spain, Switzerland and Russia sampled more than 1,100 living and dead mountain pines from the Spanish Pyrenees and 660 samples from the Altai Siberian larch Russian.
Both are highland forests that have not been disturbed for thousands of years.
The researchers used the samples to reconstruct the total lifespan and juvenile growth rates of growing trees, whether in industrial or preindustrial climate conditions.
They found that harsh and cold conditions slowed tree growth, but also made them stronger, which allowed them to live for a very long time.
But trees that grow faster in their first 25 years die much earlier than their slow-growing parents.
The negative relationship remained "statistically significant" for live and dead tree samples in both regions, according to the results.
The idea of a carbon residence time has been advanced by co-author, Professor Christian Körner, of the University of Basel in Switzerland, but this study is the first time that it has been developed. it is confirmed by data.
The relationship between growth rate and lifespan is comparable to that between heart rate and life span observed in the animal kingdom, researchers said, because animals with faster heart rates tend to grow faster but do not live that long.
Professor Büntgen added: "We wanted to test the hypothesis" live fast, die young ", and we found that for trees in cold climates, this seems to be true.
"We challenge some long-standing assumptions in this area, which have implications for large-scale carbon cycle dynamics."
The complete results were published in Nature Communications.
What can the tree rings tell us?
Trees can live hundreds, even thousands of years.
During this long life, a tree can be subjected to various environmental conditions: wet years, dry years, cold years, warm years, early temperatures, early frosts, forest fires, etc.
Concentric rings in tree trunks tell us the age of the tree and the time that it was making each year of his life.
The light colored rings represent the wood that grew in spring and early summer, while the dark rings represent the wood that grew in late summer and fall . A bright ring plus a dark ring equals one year of tree life.
Because trees are sensitive to local climatic conditions, such as rainfall and temperature, they provide scientists with information about the local climate of that area.
Concentric rings in tree trunks tell us the age of the tree and the time that it was making each year of his life. A bright ring plus a dark ring equals one year of tree life
For example, tree rings generally widen in hot, humid years and they are thinner in dry, cold years.
If the tree has experienced stressful conditions, such as a drought, the tree could hardly grow at all during those years.
Very old trees can give indications of the climate long before the measurements are recorded. This area – the study of past climates – is called paleoclimatology.
Paleoclimatologists rely on natural sources of climate data, such as tree rings, cores drilled in Antarctic ice, and sediments collected at the bottom of lakes and oceans. These sources, called proxies, can extend our knowledge of the weather and climate from hundreds to millions of years.
Combined with weather and climate information provided by satellites, they can help scientists model the major climate events that have shaped our planet in the past.
And these models can also help us forecast climate models that we can expect in the future.
SOURCE: NASA
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