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Published online 10 September 2008 | Nature | doi:10.1038/news.2008.1092
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Old forests capture plenty of carbon
Planting a new tree may be a less effective way to sequester carbon than saving an old tree from the axe.
Old forests continue to accumulate carbon at a much greater rate than researchers had previously thought, making them more important as carbon sinks that must be factored into global climate models, researchers say.
Until recently, it was assumed that very old forests no longer absorbed carbon.
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When a discpline seeks derailment of multi-$trillion world economies based upon repeated contradiction of its claimed inerrant dogma... ignore it. Conservation means somebody else in the tenebrous future deserves to consume it; and not them, either.
'"If they are carbon neutral at 400 years old, how are they going to make it to 1,000?" she asks. "If it was really carbon neutral, the trees would die."' This quote is misleading -- the ecological paradigm is not that individual trees cease to grow and become carbon-neutral over time, but rather that the ecosystem as a whole attains a balance between the death and decomposition of some individuals, and the establishment and growth of others. There are several explanations as to why even very old forest ecosystems might be measured as carbon sinks. One is that anthropogenic influences, such as rising CO2 and increased rates of nitrogen deposition, may be increasing the growth rate of ecosystems which were formerly close to carbon-neutrality. Another is that the eddy covariance method is not capturing the egress of certain forms of organic carbon from the system. Dissolved organic carbon could be leaching out of the bottom of the system, unmeasured, while CO2 comes in the top at an equal rate. Or volatile organic carbon compounds could be escaping unmeasured out the top. To confirm that mature forests are indeed carbon sinks, I agree that eddy covariance sites need more funding, to carry out soil and vegetation surveys and explicitly track the stocks of carbon over time.
Critical common sense, a much maligned and /or under utilized tool, seems to say that a tree ring in an early stage of growth represents in average a smaller volume of bio mass than in a later stage of growth. despite all the decay leaking or other mechanisms possible, this seems to be the net carbon storage of the tree. Therefor it would make sense that an older tree - all things equal - can store as much or even more carbon than a young one. This should hold true despite all "Eddy Covariance" and other real or postulated mechanisms or concepts. Since I am arguing strictly from common sense any attempt to "set me straight" is welcome.
Climax community is more stable community compared to other communities because P/R=1,nutrient cycling and energy flow is close.We can say that older communities are saturated and stable system.And any system which saturated cannot further assimilate or react as we can see even at atomic and molecular level.Further,this research will make the pooling funds towards the maintenance older forests compared to raising of new forests.Major of afforestation and reforestation programme are in developing countries which oppurtinity,avenues even livelihood for poor rural people.So,I think more research is required regarding all facet including socio-economic and enviromental issues before implementation.
I have the impression that things have been mixed up in the article and the following discussion. While I agree with the authors of the article (as well as with several other recent papers which appeared in Nature and elsewhere) that boreal forests seem to be a much more important carbon sink than previously thought, it seems that at least partly the important part of the argumentation is missing. Granted, the net ecosystem carbon balance depends on the balance between carbon assimilation by plants and its release through plant respiration and from decomposing dead organic matter. However, some recent studies indicate that not all dead organic matter undergoes complete decomposition and mineralization, ending up in carbon dioxide evolved back to the atmosphere. A number of studies, especially made in boreal forests, indicate on the possibility that part of the dead organic matter is transformed to what we call ?stabilized soil organic matter? ? the organic matter that is extremely resistant to decomposition and either does not decompose at all or is decomposed at the rate close to zero. This can be seen from some long-term studies where it was shown that none of the traditional decomposition models assuming 100% decay (even if asymptotic) does not fit the data, and instead an asymptotic model with an asymptote at less than 100% decomposition describes the phenomenon much better. This leads to the conclusion that boreal forests can be an important carbon sink even if they do not accumulate more carbon in tree biomass (as would be expected in ?climax? ecosystems). This topic is discussed more in depth in our recent book ?Litter decomposition: a guide to carbon and nutrient turnover? (Björn Berg and Ryszard Laskowski, Advances in Ecological Research 38).