MOSCOW, 15 Jun. SibFU scientists as part of an international scientific group studied how the variation of stable isotopes of oxygen, carbon and hydrogen in the annual rings of coniferous trees in subarctic regions changed over time. The data obtained make it possible to read climatic changes in the past using tree rings and to model future ones. The results of the study were published in the journal Science of The Total Environment.
Boreal (northern, from the ancient Greek Βορέας — North. — Ed.) forests cover a vast territory from 50 ° to 70 ° north latitude. In northern Canada and central and northeastern Siberia, large areas of boreal forest are also covered by permafrost, which thaws and releases additional organic carbon into the atmosphere due to rising air temperatures.
Melting permafrost and uneven subsidence of rocks and soil due to thawing of underground ice make boreal forests extremely vulnerable to climate warming.
Scientists have previously found that boreal forest trees are very sensitive to changes climate and well register the signals of summer air temperature. However, since the 1990s, in some boreal areas of the American and Canadian subarctic, a decrease in the sensitivity of tree growth to summer air temperature has been noted, which could potentially be associated with dry conditions, reduced precipitation and an increase in air temperature.
Changes in spring-summer air temperature affect the growth of trees in regions with a sharply continental climate, and information about these changes is recorded in tree rings, said Olga Churakova, Doctor of Biology, Leading Researcher at the Ecosystem Biogeochemistry Laboratory of the Siberian Federal University (SFU).< br />«
“Tree growth is also affected by other parameters such as rainfall, relative humidity, and sunshine duration. These parameters can be recorded in isotope ratios of carbon (13С/12С), oxygen (18O/16O) and hydrogen (2H/1H) in tree rings. Based on these stable isotopes and the available climate data, it is possible to reconstruct the climate back centuries and millennia,” Churakova said.
She explained that the combination of the three stable isotopes in tree ring studies could provide a comprehensive description of climate variability in boreal forests and improve the quality of temperature as well as ecohydrological reconstructions. And having reliable and high-quality information about past climate changes, you can get more accurate models of future climate changes.
June 5, 03:00
According to her, the current temperature changes in Siberia differ by 4 °C from the data of the pre-industrial period, while European chronologies and models predicted a deviation of 1.5–2.5 °C. This indicates the need for an expanded description of climate parameters and improvement of climate reconstructions, which would improve the quality of climate models and forecasts.
SFU scientists as part of an international research team have obtained comprehensive data on all three stable isotopes for the subarctic regions of Siberia and Canada. They are important for reconstructions of sunshine duration and relative humidity, as well as winter-spring temperatures that can be extracted from tree rings.
In order to make more reliable predictions, the researchers believe, it is necessary to comprehensively study past climate changes. To do this, it is necessary not only to establish changes in air temperature, but also to consider hydroecological characteristics, including the effect of permafrost in the subarctic of Eurasia.
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Scientists explained that melting permafrost and the formation of thermokarst lakes can lead to the death of trees and the destruction of infrastructure. In addition, meltwater can be used by trees during warm periods of growth, and information about this can be recorded in the isotope ratio of the stable isotope of oxygen (δ18O) in tree rings.
Today, the scientific team is faced with the task of modeling three stable isotopes in tree rings for boreal forests located both in the permafrost zone (Siberia, Canada, Alaska) and outside it (Finland, Sweden, Norway).
Necessary to model the depth of permafrost thaw and assess the adaptive capacity of forest ecosystems to changing climatic conditions, as well as to identify triggers leading to an increase in water vapor pressure deficit and a decrease in sunshine duration over the past 1500 years. One such trigger, according to scientists, is stratospheric volcanic eruptions.
The study was supported by the Russian Science Foundation (21-17-00006). SFU is implementing a strategic project «Center for Low-Carbon Development and Climate Policy» as part of the state program to support universities «Priority 2030».