Underworld holds vital clues to carbon cycle puzzle

More trees and more vigorous vegetation growth may not soak up atmospheric carbon, according to new research.

Instead, more lusty tree roots could goad the soil microbe population into releasing as carbon dioxide so much more old carbon stored in the soil.  And since the planet’s store of soil carbon is at least twice the quantity locked in the vegetation and the atmosphere, this could in turn accelerate global warming.

This is yet another example of what engineers call positive feedback, but the important word here is “could”.  The question remains open.

Benjamin Sulman − a biologist at Indiana University, but then of the Princeton University Environmental Institute in the US − and colleagues report in Nature Climate Change that they have developed a new computer model to examine what really happens, on a global scale, when plants colonize the soil and start taking in moisture and carbon from the atmosphere.

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NASA Finds Good News on Forests and Carbon Dioxide

A new NASA-led study shows that tropical forests may be absorbing far more carbon dioxide than many scientists thought, in response to rising atmospheric levels of the greenhouse gas.  The study estimates that tropical forests absorb 1.4 billion metric tons of carbon dioxide out of a total global absorption of 2.5 billion -- more than is absorbed by forests in Canada, Siberia and other northern regions, called boreal forests.

"This is good news, because uptake in boreal forests is already slowing, while tropical forests may continue to take up carbon for many years," said David Schimel of NASA's Jet Propulsion Laboratory, Pasadena, California.  Schimel is lead author of a paper on the new research, appearing online in the Proceedings of National Academy of Sciences.

Forests and other land vegetation currently remove up to 30 percent of human carbon dioxide emissions from the atmosphere during photosynthesis.  If the rate of absorption were to slow down, the rate of global warming would speed up in return.

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Scientists Track Natural Responses to Climate Change

Lumberjacks are selecting different trees, US fishermen are sailing further north to catch black sea bass, desert birds are nesting later in California and Arizona, and one kind of wildflower is changing shape in the Rocky Mountains − and all in response to climate change, according to new research.

None of these responses is simple, or necessarily ominous, and global warming is not the only factor at work.  But all are nevertheless examples of adaptation to − so far – very modest changes in temperature.

Adena Rissman and Chad Rittenhouse, of the University of Wisconsin-Madison, report in the Journal of Environmental Management that they looked at weather records and logging data and found that, since 1948, the winter interval during which ground is firmly frozen has declined by an average of two to three weeks.

Hard winters are the logger’s friend as the ground can support heavy machinery, whereas muddy soils can make tracks impassable.  So, over the decades, foresters have harvested more and more red pine and jack pine − species that flourish in sandy, well-drained soil more accessible to trucks, tractors and chainsaws.

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