Tundra forest overgrowth leads to an increase in CO2 emissions — scientists

The transformation of the Arctic tundra to the taiga, or other types of wood will result in the release of carbon dioxide from the centuries-old inventory of soil and its ability to reduce the storage of CO2, which can accelerate the rate of climate change, climate scientists say in a paper published in the journal Nature Climate Change.

Arctic "freezer"

Flora tundra absorbs a relatively small amount of carbon dioxide from the atmosphere, but with most of the CO2 remains in the organic remains, which prevent degradation low temperatures and permafrost. During the millennia of its existence in the frozen soil has accumulated a huge amount of carbon that can be released into the atmosphere in the future climate change.

A team led by Ian Hartley (Iain Hartley) from the University of Stirling (UK) to compare how efficiently store and absorb carbon dioxide tundra and birch forest in the mountains, in the northern part of Sweden.

According to researchers, the thickets of cold-resistant downy birch (Betula pubescens) are gradually replacing tundra species of vegetation on the slopes of the Scandinavian mountains and move "up" and the north. Some climatologists believe that the spread of woody vegetation in the Arctic enhances its ability to capture CO2 as birch and other trees about two times better absorb carbon dioxide.

Hartley and his colleagues tested this hypothesis by analyzing the composition of the soil of the tundra and birch forest in Abisko National Park in Sweden polar. During the cruise, climate scientists collected soil samples for each month of the year, and analyzed the volume and mass of plant remains in them.

It was found that the soil in the arctic birch forests contain a small amount of organic matter. According to scientists, twice the rate of absorption of carbon dioxide from the atmosphere can not compensate for the loss in the amount of stored the remains of plants that occur in the conversion of tundra to birch forest.

Carbon Clock

Climate scientists have tried to find the cause of the depletion of soils, calculating age and the rate of decomposition of soil organic carbon in the footsteps of radioactive carbon-14 in its upper layers. As the researchers note, multiple testing of nuclear explosive devices, and development of nuclear energy for the last 50 years has led to the saturation of the atmosphere with carbon-14.

Plants absorb this isotope is on a par with the "normal" carbon-12 and its atoms get together with other organic remains in the soil. A high proportion of carbon-14 indicates that the deposits were formed relatively recently, during the "nuclear age", and the low — the age-old nature of their formation.

Hartley and his colleagues found that the soil of birch wood is almost no organic remains, formed before 1950. This means that they have been washed out of the soil after the conversion of tundra to the forest, and for the lifetime of the birch forests in soil accumulated a small amount of carbon.

The situation is aggravated by the fact that plant roots stimulate the collapse of the old organic matter in deep water, which is reflected in the characteristic peaks in the concentration of carbon-14 during the intensive growth of birches in July and August. This explains the unusually low proportion of carbon in the soil of the Arctic forests.

Thus, the transformation of the tundra in the Arctic forest not only leads to a decrease in the ability to store carbon in the soil, but also to the release of old stocks of organic matter, which turns later into carbon dioxide and other greenhouse gases. This can lead to a significant acceleration of climate change, the scientists conclude.

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