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Global Change Research Institute, CAS

Amount of carbon stored in forests reduced as climate warms

The accelerated growth of trees caused by climate warming does not necessarily translate into higher carbon storage. This is suggested in a study by an international team of scientists led by prof. Büntgen, who works at the Global Change Research Institute CAS as well as at the University of Cambridge, published in the journal called Nature Communications. The team found that as temperatures increase, trees grow faster, but they also tend to die younger and the carbon they store is returned to the carbon cycle sooner. Thus, the carbon retention time is shortened. This result can change the perception of how the global carbon cycle works. This notion assumes that faster tree growth in the anticipated future climate conditions will lead to higher carbon deposition in the forest through photosynthetic CO2 fixation, which will help reduce the anthropogenic greenhouse effect. Based on this paradigm many institutional and governmental measures have already been taken having extensive political, ecological and economic consequences.

The scientists tested the hypothesis stating that in trees “faster growth means shorter life” which is generally valid in the animal kingdom, where there is a correlation between the pulse rate in animals and their lifespan. For the study, they chose trees growing in unspoiled environment at high altitudes where carbon can be stored for centuries. These were represented by pine trees from the Spanish Pyrenees and Siberian larches from the Altai Mountains in Russia.

They used the information contained in tree rings in order to be able to study past climatic conditions. The width, density, and anatomy of each ring contains information about the climate of the past year. By taking core samples from living trees and disc samples of dead trees of various individual age categories, the researchers were able to reconstruct how the Earth’s climate system behaved in the past and understand how ecosystems were, and are, responding to temperature variations.

The results obtained from the samples of both living and dead trees, from both regions studied, showed that harsh and cold conditions cause tree growth to slow down, but simultaneously trees are stronger and live longer. Conversely, trees that grow faster during the juvenile stage will die much earlier than their slowly growing relatives. At the same time, the study results confirmed the premise of prof. Körner – one of the co-authors of the study – about the limited carbon retention time in biomass.