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I've read that forests are important because they absorb carbon dioxide and release oxygen to the atmoshpere 1. But other places say that this is false for a mature forest:

"On average, then, this mature forest has no net flux of carbon dioxide or oxygen to or from the atmosphere, unless we cut it all down for logging," Sarmiento said. "The ocean works the same way. Most of the photosynthesis is counterbalanced by an equal and opposite amount of respiration." 2

It seems that phytoplakton are the responsibles of carbon dioxide fixing and oxygen emission.

Tiny ocean plants called phytoplankton contribute 50 to 85 percent of the oxygen in Earth’s atmosphere.3

So are there any solid studies that show what are the "lungs" of the planet, if any?

jinawee
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    Is http://skeptics.stackexchange.com/a/6804/2703 a satisfactory explanation, or answer to your question? – ChrisW Aug 10 '13 at 22:08
  • one thing to note about a mature forest is that the trees will die fall and decompose and new ones will replace it, this will produce oxygen (or more accurately bind carbon) – ratchet freak Aug 11 '13 at 13:08
  • @ratchetfreak: Yes, this is the essence of the answer pointed to by ChrisW. I'm hoping we can close as duplicate. – Oddthinking Aug 11 '13 at 13:10
  • Yes, mine's a duplicate. Should I delete the question? – jinawee Aug 11 '13 at 13:32
  • @ratchetfreak My guess is that when the forests' total biomass is constant (e.g. when the planet's forests are mature and stable) then carbon and oxygen aren't affected either way. When the biomass is growing, as it did when plant-life first evolved and grew all over a previously-barren planet, that binds CO2 and produces O2 (more specifically, "produced" in the past tense). When the biomass is shrinking, as when humans deforestate, that releases CO2 and loses oxygen. – ChrisW Aug 11 '13 at 15:41
  • @ChrisW biomass increases in more subtle ways: dropped leaves and branches adding to the topsoil would be the one that comes to mind – ratchet freak Aug 11 '13 at 16:16
  • @ratchetfreak I've heard that forests have little soil, and that any dead biomass (leaf litter) is consumed and recycled. – ChrisW Aug 11 '13 at 16:45
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    @jinawee No need to delete it. It will get closed as a duplicate, but leave it here as a signpost for search engines. –  Aug 12 '13 at 08:11
  • I've voted to close it as a duplicate, therefore. – ChrisW Sep 11 '13 at 09:30

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