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Comment by bcbrown | Hacker News Reader

> Once trees have grown tall enough, they tend to slow down, so you'd expect them to not grab as much carbon anymore.

I don't think that's accurate (or at least not very precise). Studies have shown that when evaluating the metric of annual addition of tree mass per acre in the rainforests of the Pacific Northwest, old-growth forests add as much or more when compared to "young" forests.

I don't have any specific sources, but if you want to know more the research by Robert Van Pelt should be a good starting point.

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This is definitionally untrue. Forests have a maximum biomass carrying capacity, and they rarely reach that capacity, instead losing carbon to stochastic events like fire. Old growth forests "store" a lot of carbon, but their capacity to sequester is finite.

https://www.fs.fed.us/psw/topics/fire_science/ecosystems/car...

You're not listening to what I'm saying. I'm not talking about carbon sequestration, I'm refuting the argument that "once trees have grown tall enough, they tend to slow down". Here, I pulled a source for you: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.45...

> Wood production of the entire main trunk and whole crown both increased with size and age up to and including the largest and oldest trees we measured.

This is even supported by your own link:

> In the past, some researchers have suggested that converting old forests to young, fast-growing plantations, whose harvested wood products could store carbon for several decades, would create a net increase in long-term carbon stocks. This approach was based on the idea that old forests are slow growing and thus carbon sequestration slows down as forests age. More recent research generally does not support this idea, as a global survey of old forests found that many continue to sequester carbon and have stocks that far exceed young, managed forests.

Of course they have stocks that far exceed young managed forests (they store a lot). But forests do not continue packing biomass on indefinitely (the rate of sequestration slows and eventually stops). See this summary of Malmshmeimer (2011) [1]:

“Trees do die, and at a rate that eventually reaches some kind of a stasis at a landscape level,” says Fried. “In some stands, up to one hundred percent of the trees will be killed by a fire or insect outbreak; other stands con- tinue to grow, but over the entire forest you’ll eventually reach a plateau, after which the net in-forest growth and carbon accumulation rates decline—eventually to zero.” Many pro- tected forests on public lands, especially those in parks and wilderness areas, are no longer increasing carbon storage, he says.

[1] https://www.fs.fed.us/pnw/sciencef/scifi155.pdf

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