i have some trees i think are poplar/cottonwood, so im told where i live in fairbanks alaska. they are all roughly 30ft high. the bark at the bottom is rough like some cottonwood i have seen. about 8-10 ft up the tree it changes to a greenish gray color that feels waxy almost. when i cut it the very center is almost black to dark brown (no more than 3-4 inches in diameter on bigger trees with overall diameter of 18" or more) with white around it. It feels very heavy like it is water logged especialy after being cut when green. more than the birch i am used to cutting. i dont have any pictures yet just wondering if any one had a good idea what it might be.