[garmaine]

You don’t need a source. To be a net emitter the tree would have to be losing mass. That’s not what healthy trees do, even old ones.

I believe the article might have been trying to say is that trees tend to die and decompose (or burn) which makes them carbon emitters.

[benj111]

You're talking about individual trees though.

Theres plenty of mechanisms where the individual trees grow, but the forest holds less carbon.

The linked article [1] mentions forest fires and insect infestations.

[1] https://www.cbc.ca/news/canada/calgary/canada-forests-carbon...

[garmaine]

I other words, trees dying...

[benj111]

Right..... What's your point?

[Robotbeat]

That’s not true. Methane is a significantly more potent greenhouse gas than CO2, so if the tree is absorbing CO2 but the decomposing needles and leaves are emitting methane, it could easily be a net GHG emitter.

[garmaine]

Trees don’t produce CH4 (except in decomposition).

[benj111]

"but the decomposing needles and leaves are emitting methane"

[garmaine]

Ah, true. I hadn’t thought of droppings off the tree. (Comment was edited I think, or I seriously lack reading comprehension.)

[jefftk]

If a tree keeps growing, but also gets more successful at suppressing growth of it's neighbors, then it can be a net emitter overall even though it's a net absorber considered individually.