wylie
Level 3 Rank
Posts: 129
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Post by wylie on Mar 14, 2009 18:52:53 GMT
I agree that even mature forests sequester significant amounts of carbon (not as much as a young forest but still significant). If you wander through-out the young (or old) forests of North America (and northern Europe), you will inevitably be walking on a few to several meters of topsoil of which a significant fraction is cellulose or cellulose breakdown products. All (or nearly all) of that topsoil was built up since the last ice age since in Northern North America (and Northern Europe) those areas had been scoured clean to bedrock (and into the bedrock) by ice sheets a couple of km thick as recently as 12,000 years ago. Less than 12,000 years to produce a metre of mostly carbon (by weight) by the action of plants and animals is a formidable rate of carbon sequestration (and some of it by "mature forests").
Ian
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Post by nautonnier on Mar 14, 2009 19:03:37 GMT
"Mature" forests are very rare - when you factor in Volcanic activity, forest fires and other large scale events (i.e Ice ages), few forests have the required several thousand years to reach maturity. Many trees can grow for 1000's of years (NZ Kauri for one) but tend to get beaten by geology (buried in swamps when the land sinks, etc etc) Bingo! Mature forests in theory are carbon neutral. But as one poster has pointed out there are continual carbon sequesterization going on on the forest floor. Its very noticeable when you visit a mature redwood forest you find a top soil sometimes meters thick filled with wood fibre. It might be unique to the anti-rot nature of redwoods but a completely mature redwood forest if there is any is really really old. The fact is carbon sequesterization in a forest is a curve starting from zero reaching af maximum rate of carbon sequesterization, then the rate gradually declines towards zero though short of a disaster for the forest, fire, disease, etc. it probably never actually reaches zero. But despite that there is an opportunity for carbon sequesterization from cutting forests. But I am for sequestering it based upon demand for products not biochar. The respiration of the tree is generating CO 2 from the sugars oxidized by O 2 at a rate equivalent to or faster than the leaf mould can build up. Not only that but the tree is continually transpiring water vapor which has a 'radiative forcing effect' an order of magnitude higher than CO 2. Remember that the AGW hypothesis depends on increasing water vapor to actually do the real warming. A mature deciduous tree can transpire its own weight in water in a day - EVERY day. So to sequester a tree's weight in carbon you emit that weight of a green house gas 10 times more effective at radiative forcing every day of the tree's life. AGW proponents seem to have a blind-spot in their AGW hypothesis it seems that they only think water vapor matters if it is as a result of 'feedback' from CO 2 'warming' - but you should try thinking through the actual logic.
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