LONDON - In the largest experiment of its kind to date, ecologists have found that the wetter the Arctic tundra becomes, the more carbon dioxide (CO2) it gives off.
According to a report in Nature News, if the tundra becomes increasingly warm and wet, which is anticipated as global temperatures rise, it might emit more carbon than expected.
“It’s a big deal,” said Walter Oechel, an ecologist at San Diego State University in California and principal investigator on the study. “These are aspects that haven’t been recognized before,” he added.
The Arctic region locks up large amounts of carbon in its soil and permafrost, and researchers are working to tease out the complex relationships that might govern what happens to that carbon in a globally warmed world.
So, Oechel’s team set out to deliberately manipulate the water table of a portion of the tundra.
The team chose as their test site a 1.2-kilometre-long lake in the North Slope region of Alaska.
Using plastic dikes, the researchers divided the lake into three parts.
From the centre third, they pumped water into the northern third, leaving the northern part extra soggy and the centre portion dry. They left the southern part untouched, as a control.
Instrument towers, one above each portion, gathered data on the emission of trace gases such as methane and CO2.
The team thought that the higher water table would probably mean less CO2 entering the air.
Rising water drowns both the vegetation and the ‘aerobic’ microbes that rely on oxygen to decompose the plant matter, giving off CO2 in the process.
So, the greater the depth of water above the surface, the less oxygen and light penetrates to stimulate microbes in the soil beneath, hence presumably resulting in the release of less CO2.
But, measurements from the partitioned lake showed the opposite: the northern, flooded portion of the lake gave off more CO2, becoming a carbon source, whereas the drained portion and the control portion remained as carbon sinks.
“Apparently, anaerobic microbes in the soil - those that don’t require oxygen but can still produce CO2 - thrived under the drowned land,” said Oechel’s colleague Donatella Zona.
This suggests that hydrological changes in the Arctic could have “unexpected results - huge amounts of carbon in the soil could be released to the atmosphere even under completely anaerobic conditions,” she added. (ANI)
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