What part of a dead tree doesn't biodegrade

[tonyjeffs]

With so much in he news about climate change, I was wondering whether a tree, having removed CO2 from the atmosphere during its lifetime, sends all of it back into the atmosphere when it dies.

A dead tree will be broken down by bacteria+c and the carbon it's molecules contain converted to CO2 through respiration. Why would some of the carbon in the tree escape this process, so that over the years it can become limestone or coal?
What would be the mechanism?

Thanks

[Linn]

You mean the process of petrification?

[mith]

It's buried and compressed...and limestone isn't carbon, it's calcium.

[tonyjeffs]

I think the answer is to do do with acidity in the soil/earth which occurs sometimes. e.g. peat, or humus contain chemicals that stop the action of insects and bacteria, so in those circumstances the tree doesn't biodegrade.

Mith
Limestone CaCO3. Does contain carbon; but your right inasmuch as it probably isnt relevant to trees. More sea shells.

Lynn, yes; I mean 'What protects the wood from biological decay?', so that it can stay around long enough to become petrified.

The point is that if trees were to completely biodegrade, returning all the CO2 to the atmosphere, the argument that they protect against global warming would be invalid.

Tony

[Linn]

Petrification doesnt keep a tree from decaying,
minerals replace what was there and retain the shape.

The co2 that is released back
is not greater than the co2 that is absorbed

A good discussion here:
http://www.calforests.org/the_news_room ... Change.htm

[satrohraj]

With so much in he news about climate change, I was wondering whether a tree, having removed CO2 from the atmosphere during its lifetime, sends all of it back into the atmosphere when it dies.

A dead tree will be broken down by bacteria+c and the carbon it's molecules contain converted to CO2 through respiration. Why would some of the carbon in the tree escape this process, so that over the years it can become limestone or coal?
What would be the mechanism?

Thanks

I think everything is biodegradable..
But i read somewhere that it changes into coal (after buried inside the earth)

[mith]

They are biodegradeable, but that doesn't mean that the argument of protection from global warming is invalid. A living tree isn't decomposing, it's only when it dies that it's released. Perhaps it's not a permanent solution but it's a renewing one..

[AstusAleator]

The vast resources of coal and oil that we have been tapping into for the past couple of centuries are examples of where this carbon goes after being bound by photosynthetic organisms.

Carbon can be "removed" from the cycle largely by geologic and hydrologic processes. In the case of trees, events such as landslides and floods can cause whole forests to be covered or be put into an otherwise abiotic/anoxic environment, in which the molecular carbon cannot be converted to gas.
Or, in the case of pete-bogs, trees growing in said bogs will simply fall into them.
Furthermore, trees are only one part of active ecosystems. When they die, they will be consumed or broken down by a plethora of organisms, which will then convert the carbon to new forms (granted, some of it will become gaseous). Ultimately, much of this carbon finds its way into the soil (acid leaching takes it beyond the a-horizon).
Also, much of the carbon is drained off into streams and rivers, and ultimately is deposited in alluvials, lake bottoms, or the ocean.

So no, not all of the carbon bound by trees is re-released back into the atmosphere. Even in the cases of wildfires, much of the remaining ash (including the airborn) is primarily carbon, and will make its way into the soil layer or to the bottoms of bodies of waters.

[Navin]

Then it is important to note this irony - that whilst plants served to remove carbon dioxide in the air (especially the petridophytes long time ago) that are then are converted to coal (therby contibuting to global cooling) is now implicated in global warming when the coal (from those plants) is being dug up and burnt.

[fscottdahlgren]

The atmosphere is dynamic. Photosynthesis supports concentration gradients that we rely on. Once carbon is removed from the atmosphere, rest assured, it will eventually find its way back. Trees burn oxygen and release CO2, too. Possibly, by dieing the tree makes room for another individual who will photosynthesize more quickly. Or, a strip mall.