If it doesn't burn, it turns into soil eventually, and that keeps it mostly sequestered.
I haven't looked into how much of the carbon stays in the soil and how much is recycled into other organisms as they decompose. I'm just remembering how fire makes carbon & other nutrients available again in some ecosystems and wondering if there are fungus and bacteria that do the same in ecosystems without fire. If I'm remembering right, most fossil fuels started in bogs or other aquatic places where plant matter was buried before the usual decomposition happened.
Right. But the carbon still had to be in the deposit. At this point I'm speculating that if the trees in a forest [no fires] sequester X tons per year for Y years [longer than lifetime of trees], the Total Sequestered Carbon << X×Y, unless something is done to prevent typical decay. I think most of the carbon cycles and not much is sequestered once the forest is mature. Though now I'm realizing that the zero-to-maturity sequestration is probably more important than the post-forest-maturity sequestration.
Not a mycologist, but I've heard some speak, and fungus is a major component in breaking down biomass, especially wood.fungus