Magazine article Science News

An Unexpected Release of Carbon Dioxide

Magazine article Science News

An Unexpected Release of Carbon Dioxide

Article excerpt

For scientists trying to predict future climate change, the role oi vegetation and soils remains a thorny issue. Some believe the two will slow global warming by absorbing substantial amounts of carbon dioxide now accumulating in the atmosphere from the burning of fossil fuels. Others think the warming will cause plants and soils to release more carbon dioxide, exacerbating the problem. A new report from Russian scientists raises the ante on this question by suggesting that Siberian soils emit much more carbon than previously realized.

While plants store carbon dioxide through photosynthesis, microbes in the soil release this greenhouse gas by breaking down organic matter in the dirt. That much of the carbon cycle is clear during the summer, when the sun is strong and the ground surface unfrozen. But what happens when winter comes to the far northern latitudes? Biologists had presumed that microbial activity grinds to a halt when the ground freezes solid, just as photosynthesis shuts off when the sun disappears. But S.A. Zimov from the Pacific Institute for Geography in Vladivostok and his colleagues report that microbes remain busy releasing carbon dioxide long after winter arrives.

Zimov's team measured carbon dioxide emissions from the soil at a site in northeast Siberia, 100 kilometers from the Arctic ocean. Although the gas production varied substantially, depending on the place and time of measurement, the soils released an average of 13. …

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