Futurology

But you need to cut those trees down and place them somewhere they won't rot

Sink them to the bottom of the deep ocean, but trees famously float

Leave them in deserts where the dryness will suppress rot, but damage the desert habitat

Dump them in peat bogs, but there aren't enough

Perhaps it would be best to cook them to charcoal, it releases some carbon into the atmosphere, but it would leave some solid, inedible to anything carbon that can be dumped in any old mine, but that's expensive

Also if you dump the whole trees in whatever way, you also dump whatever nutrients are in it