I'm just on the other side of the lake from that part of Canada. I cut a few rowan/mountain ash staves this winter. The type found here has a smooth purplish bark I would consider almost shiny. The ones I harvested had more sapwood than heartwood. Also that stave looks like it came from a rather large tree. I've never seen a mountain ash with a trunk diameter of more than a foot or so.
If I had to guess with just those two photo's to go on, I'd say mockernut hickory or ash based mainly on the bark pattern. Factor in the heartwood color, I'd say it's mockernut hickory. Burn some and take a whiff. If you get hungry, it's hickory. If you can return to where the stave was cut, search the ground for hickory nut shells for a final determination. I've made both ash and hickory bows, my ash limbs were thicker compared to a hickory bow of the same weight. The ash bows were lighter as well, even though they had more wood/volume. Both make fine bows, but it helps to know what dimensions you're aiming for before you start or you might run your cabinet scraper down to a nub.
