The oaks, how subtle and marine! Bearded, and all the layered light Above them swims; and thus the scene, Recessed, awaits the positive night.
Just in case you didn't get it from the title ("Bearded Oaks"), Warren begins this poem with the subject, straight up. We're talking about trees. Start with the real, the thing, then get ready for layers of meaning and abstraction—that's his way. On the straight side, we've got trees looking like something from underwater, the light swimming above them, while the scene waits for night.
To the oaks, he adds two adjectives: "subtle," a kind of judgment suggesting a delicacy you can see only if you look very intently, and "marine" to suggest that things look submerged.
Line 3 gives another description, also from the title: "bearded." This plays on the look of the Spanish moss hanging from these trees, which makes them look like giant Gandalfs what with their grey beards and all. Don't take our word for it, though.
Check one out here. You can imagine the speaker's eye moving up, past the trees, their hanging beards of moss, on up to "the layered light" swimming above the trees to keep with the watery description.
There's a shift midway through this line with the semicolon (watch for punctuation in this poem—it's another Warren signature) and a much fancier proclamation, "thus the scene." The diction jumps a level to the more dramatic or academic. The speaker has shown himself with the announcement of "the scene," because the place is just a place until it's seen by people who make it a scene.
So, what kind of scene is it? "Recessed"? This word has at least two meanings: 1. set back, secluded, and 2. suspended or delayed. Both meanings work to describe this scene that awaits "the positive night."
Before we get to that night (so positive), we should also just mention that the word "scene" suggests a play, or at least a director. We're left to wonder who might have arranged all these things at which the speaker is looking.
Back to the night: it's coming and the scene waits for it. This is some personification—after all, scenes don't really wait like a person at a bus stop, right? As well, this night is said to be "positive," with that word's many meanings. No doubt the speaker means to suggest that night is a good thing, different from, you know, a scary night filled with chainsaw murderers. Also, the word carries the sense of certainty (i.e., "I'm positive I left my wallet right there on that street corner, now where did it go?").
With this first stanza, a rhyme scheme has come together (we knew this poem could do it). It's ABAB, where the letters stand for the end rhyme of that particular line. We also get a mostly iambicmeter. These formal elements add a touch of grace and grandeur, really classing up the joint, just in case words like "subtle" and "thus" hadn't done the trick. Check out "Form and Meter" for more.