How about the assumption that after an initial period of increasing growth, the mass growth rate of individual trees declines with increasing tree size?
Yes, a few days ago on Eurekalert:
http://www.eurekalert.org/pub_releases/2014-01/osu-ota011314.php
http://www.eurekalert.org/pub_releases/2014-01/stri-tgf011514.php
Regards,
Joachim
Thanks Joachim, yes i found this paper in Nature journal.. So the trees will be grow until death?can we make generalition or just in the specific species?how about assumption that in older tree, photosynthesis product used for recovery not for growth..
Hi Wahyu,
in the paper mentioned by Joachim the authors analyze over 400 species distributed worldwide and found a continuous and increasing growth (and therefore C fixation) with age in over 90% of these species. So yes, I will say that the assumption that older individual trees stop fixing C does not seem to hold at all.
best
Tree or forest scale? The difference on the scale of forest however is that no tree is eternal – like all living things they have a lifetime, and will eventually die and decompose, releasing a proportion of the carbon back into the atmosphere as CO2.
In mature forest the rate of death and decomposition is quite clearly balanced with the rate of new growth – the total number and size in a mature forest is stable, and therefore the total carbon held is stable – trees come and go, but the total composition of a mature forest does not change without outside interference, and therefore the carbon held will not change either.
The accumulation of carbon in trees more so in tropical trees depends on the ratio of P/R i.e. photosynthesis to respiration. This ration has been observed to be high in younger trees. Therefore, the carbon accumulation is high in younger trees. But as the trees grow, the tree size increases, leading to increased respiration. Hence, the ratio P/R decreases. The trees growth freezes no sooner P/R ratio becomes 1.
the results in the nature paper says the P/R ratio i always >1 , so it means that forest biomass must be limited by tree mortality.
What I have mentioned earlier for a normal tree growth. But yes, if for some reason, the tree mortality sets in at younger or growing stage, the P/R ratio may tend to less than one.
It may even happen in over grown trees as mortality do set -in in over grown trees.
I agree with Rudiger, these are important points that could be worth looking into further!
Yes, I agree with you Rudiger and Oskar...
the point is different scale, single trees and stand...
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