There's some research that shows that burying logs super deep (beneath the biologically active layer) is an effective method of long-term sequestration: https://pubmed.ncbi.nlm.nih.gov/35362755/
Well, not a mature forest, but one of those "tree farms" of evenly spaced monoculture sounds like it'd be a great candidate.
Of course, since those tree farms are explicitly for production and therefore owned by the owner class, who don't really want anything to do with this whole unprofitable "saving the planet" thing, the above scenario is more likely -- but all I meant to suggest is that it'd be possible to use this method and not destroy precious biodiversity at the same time.
Man, environmentalism sure has changed a lot over the decades...