are the best? We already have land with a few hundred trees-mostly native oaks. (Temperate zone-mild winters/hot summers-mid-United States) I want to plant a few more, and replace some that are damaged or not doing well. I heard apple trees are really good at cleaning the air. Is that true? What others?
Thanks in advance. By the way--we just set 2 new records for high temperatures in January--70 and 72 degrees!

If thats really what you want to do about GW, then the answer is pretty straightforward: plant whichever tree grows the fastest in your area. Because every pound of tree you get represents roughly a pound of carbon removed from the atmosphere.

Awhile back I heard that the Box Elder was a very fast growing tree, and was recommended for an impoverished area which needed to grow lumber in a hurry.

when a tree dies, it release all the carbon it collected over the years

Trust me, leave the area alone! I presume there is no grazing pressure stopping natural regeneration.
And if that is the case, natural regeneration will provide much better quality stock than your suggested planting.
That’s of course if you what a more natural, nature friendly space.
Unless you have invasive foreign species I would suggest leaving alone.
Marvel at the beauty of the trees in all states. Far too often people remove dead and dying trees.
Unless your tree is in an area which is of risk of causing harm to person or property let them stay.
This is a shame as they provide habitat for many species in the food web.
If you are determined to plant, make sure the planting stock is native, and of known provenance.
I am a Chartered Forester and would be glad to expand on this subject if you emailed me.
Regards