Old-growth forest carbon sinks overestimated

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Lucas
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Old-growth forest carbon sinks overestimated

Post by Lucas » Fri Mar 26, 2021 10:17 am

https://phys.org/news/2021-03-old-growth-forest-carbon-overestimated.html

Refutes some theories.

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dbhguru
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Re: Old-growth forest carbon sinks overestimated

Post by dbhguru » Sun Mar 28, 2021 11:26 am

Lucas,

Thanks for bringing this study to our attention. It is a good topic for discussion. I think that there is value to the study so long as it isn't interpreted as applying to all forests. West Coast big tree forests are far from a steady state at 300 years. In addition, while old trees slow their growth significantly, what we call old growth forests are really multi-aged and as disturbances set at least parts of them back successionally, I think generalizations about assuming steady state conditions are usually risky.

For white pine stands in the New England area, especially southern New England, growth at the stand level on a good site appears to be greatest between 40 and 80 years. From 80 to 120 years, period growth slightly exceeds that for the first 40 years, and from 120 to 140 years, growth outstrips 0 to 20. Individual pines continue growing productively for 160 to as much as 200 years, and occasionally longer. However, in all stands, as we commonly see, there are winners and losers. The dominants increasingly carry the load as the stand ages. For young stands there's strength in numbers. I've seen studies that maintain that the total growth at stand level is greatest between 20 and 40 years. I can't say that for the stands being studied, that wasn't the case, but I can say that it isn't true for the vast majority of forests in the eastern U.S. On the other hand, eastern forests over say 300 years in age are certainly not growing faster than when under 30 years, but the debate goes on.

Once under-ground carbon stocks are depleted, building them back up is a slow process. This works against clear cuts. However, silvicultural plans can lead to more carbon being sequestered annually than if left to Mother Nature. However, these plans must be designed specifically for that purpose. There is no having our cake and eat it to long term strategy.

Measuring carbon stocks and rates of increase and loss is done through complex computer simulations. I spend much of my time these days following the story of individual trees, small clusters, and at the stand level. I test individual volume-biomass models and find myself overwhelmed in trying to sort through the conflicting studies.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

MarkGraham
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Re: Old-growth forest carbon sinks overestimated

Post by MarkGraham » Tue Mar 30, 2021 9:10 pm

The best forestry practices to fight the Industrial Age increase in atmospheric carbon:
1. Double stand rotations, in other words let trees get bigger in managed forests before they are cut.
2. Assist countries having large amounts of tropical forest to not slash and burn for new farm land but instead make existing farm land more productive.

Point 2 could also help prevent future animal to human virus transmission. Not sure about Covid, but certainly Ebola, AIDS, and SARS COV-1 arose from tropical forests.

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