I'm not real picky, and I don't get some of the wood many of you all get due to our soil here. My pic post back in 2, I was splitting "sweet gum" which splits just as bad if not "WORSE" than elm. I'll burn just about any wood except pine! If it's hard, I'm burning it. I get lots of Maple here, especially after any substantial storm, sandy soil means lot's of trees going down.
Heading out to knock down more trees. I am not a scientist so I'll leave this task up to you professionals. See if you can find out if there is a direct correlation between root structure and BTU output of trees. Seems the soft low btu trees jump out of the ground but I have been known to spend an hour trying to move a white oak. I'll be back later to see your input.
I thought you all might find this relevant. I just ran into some standing dead red elm. This round was about 17" Not the easiest to split but not terrible either.