The bark on young trees is smooth and white to greenish or dark grey, and often has conspicuous lenticels; on old trees, it remains smooth in some species, but becomes rough and deeply fissured in others.

Learn something new every day. In America the dominant species of poplar are grandidentada (big tooth) and tremuliodes (quaking), both of which maintain smooth bark into maturity. I also learned that the crowns of those (likely black) poplars is 35m up, so we absolutely aren't seeing leaves from the trucks pictured. The maple leaves in the picture are likely from understory saplings or sub dominant mature trees.