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American Association for the Advancement of Science

Can ancient forests help slow climate warming?

The trees in the Dinghushan Biosphere Reserve, which is in China's Guangdong Province are really old. As in 400 years old! Chinese scientists have now discovered that this ancient forest soaks up carbon from the atmosphere much faster than they expected.

The researchers describe their findings in the Dec. 1 issue of the journal Science.

The Dinghushan forest is an "old-growth" forest that hasn't been disturbed by human activities like logging or road-building.

Scientists all over the world are trying to learn what happens to carbon after it has entered the atmosphere. The Earth has many natural processes that release carbon into the air, such as rotting, or as scientists say, "respiration," which occurs when bacteria and other microscopic organisms break down leaves and other vegetation.

Humans are also responsible for adding carbon to the atmosphere. Cars, factory machines, and other things that burn fuel also release carbon dioxide. As you probably know, this extra carbon dioxide and other greenhouse gases in the atmosphere is causing the Earth's climate to warm.

In order to plan for this change and to find ways to reduce the amount of extra carbon in the atmosphere, researchers need to know all the processes that add carbon to the atmosphere (carbon "sources") and those that remove it (called carbon "sinks").

Guoyi Zhou of the South China Botanical Garden in Guangzhou, China and his colleagues have found that the old-growth forest of Dinghushan is an important carbon sink.

This is surprising, because until now, scientists have generally thought that old-growth forests weren’t important carbon sinks. They thought that the amount of carbon that the trees soaked up from the atmosphere (through photosynthesis) was roughly the same as the amount given back to the atmosphere through respiration.

Dr. Zhou's research team measured levels of organic carbon in layers of the soil in the Dinghushan forest and found that the soil accumulated atmospheric carbon at an unexpectedly high rate from 1979 to 2003.

The scientists say they don’t exactly know why so much carbon from the atmosphere has built up in the soil. More research is needed to answer that question and to study how old-growth forests respond to environmental change.