The speaker is standing in fog, or low cloud, that the wind keeps pushing past. In the middle of it, they smell wood smoke, a small sign of human life that arrives without any visible source. The poem never says where the smoke comes from, which makes the moment feel faint and a little uncertain.
The second stanza turns to the ground. The tracks, probably in snow, have melted until they're just "erasures." They no longer show who or what passed by, only that something did. Then the poem shifts with "except for the trees." The trees stay put, "marooned on the same / round islands," which suggests the bare circles of ground around their trunks, left clear as the snow shrinks away.
The mood is quiet, damp, and reflective. Everything moves or fades, yet the trees hold their place. The speaker seems to watch this with calm attention, noticing how little remains of the past, and how steady the things that stay are.