Thou, from whose unseen presence the leaves dead Are driven, like ghosts from an enchanter fleeing (2-3)
The second image of Shelley’s "Ode to the West Wind" involves not one but two references to death: the "leaves dead" that are strewn over the ground in autumn, and the "ghosts" of which they remind us.
O Thou, Who chariotest to their dark wintry bed
The wingèd seeds, where they lie cold and low, Each like a corpse within its grave, until Thine azure sister of the Spring shall blow
Her clarion o'er the dreaming earth, and fill [. . .] With living hues and odours plain and hill (5-10, 12)
The West Wind plants seeds in the ground in the autumn that will germinate next spring. But the seedbeds are like graves, the seeds are like corpses, and their transformation in the Spring is like the resurrection of bodies during the Apocalypse. The Spring wind even blows a "clarion" that reminds us of the Last Trumpet. Even the quickening of life in a tiny seed reminds Shelley more of death than it does of birth.
Of the dying year, to which this closing night Will be the dome of a vast sepulchre (23-25)
If the West Wind is a dirge and the autumn night is a tomb, then who is the corpse? The speaker? Nature? The entire world? All or none of the above?
If I were a dead leaf thou mightest bear (43)
Not only does this remind us that the speaker is obsessed with dead leaves, it reminds us that "leaf" could mean a page in a book as well as something that dropped from a tree. If the speaker is a poet, as he implies, then his obsession with "dead leaves" might have more to do with his own writing than with Nature.
Drive my dead thoughts over the universe Like withered leaves to quicken a new birth! (63-64)
Death always results in resurrection in this poem; even though the speaker doesn’t anticipate that he himself will be resurrected, he believes that spreading his own "dead thoughts" around will create an opportunity for new ideas to be developed.
If Winter comes, can Spring be far behind? (70)
It’s important to read this as an open question. For the West Wind, which is autumn’s breath and ushers in the winter, spring is always on its way; for the speaker, though, whose "Winter" is more metaphorical, it’s entirely possible that his ideas, or even the intellectual current of the world, could wither away and not be renewed. He hopes that the death of some ideas and philosophies means that we’re about to come up with some better ones – but he’s not certain.