How does the poem bring out the relationship between man and nature?

William Carlos Williams's modernist poem "Spring and All" does not explicitly describe the relationship between man and nature. The only real reference to the human world is at the very beginning of the poem when Williams references "the contagious hospital" in line 1. Williams was a doctor in addition to a poet, so he could be referring to observations he has had when going to or from his work at the hospital. The human observer expresses his attitude toward nature and specifically spring, but his relationship with nature is only implied.
The speaker describes nature in winter, with spring approaching. Of the trees the speaker observes, he says,

Lifeless in appearance, sluggishdazed spring approaches—They enter the new world naked,cold, uncertain of allsave that they enter. All about themthe cold, familiar wind (14-19)

The trees are "lifeless" and "uncertain" now, but as spring approaches, "objects are defined" (22). The spring will give nature a more solid identity. The speaker elaborates on this idea in the last several lines of the poem:

But now the stark dignity ofentrance—Still, the profound changehas come upon them: rooted theygrip down and begin to awaken (24-27)

This "profound change" that spring bring with it allows nature "to awaken." The way the speaker phrases this truth makes it sound like the trees will come into their own, embracing and defining their identities in a way that is not possible in winter when they are so new and "uncertain." The speaker describes the trees almost as though they have a human identity and are capable of understanding their power and potential. The speaker is inspired by his observations of nature to consider metaphysical concepts such as life and death.