Trembling Aspen (populus tremuloides)

Broadleaf, deciduous, flowering tree, generally to 20 m, occasionally to 28 m high; trunk slender, cylindrical and branch-free for most of its length in forest sites, generally to 25 cm in diameter but may reach 60 cm; crown short, narrow and rounded; roots shallow, widespreading and producing new shoots from root suckers.
Source - NEST Field Guide FG-001