Three lines, no punctuation, no capital letters, and the speaker doesn't show up until the very end, only to fall asleep. That ordering is the poem's quiet joke and also its main idea. Dave Bonta's "Nocturnal" is about a world that carries on working without a witness, and it makes the point by placing the human being as late, as small and as unconscious as grammar allows.
The whole poem is one comparison: "the night wood / is as full of business / as a clock when I am asleep". It looks like an odd pairing, since a wood grows and a clock is assembled. But the two behave alike in the dark. A clock keeps going whether or not anyone is looking, and we only really hear it in a silent room. Once we sleep we hear nothing at all, and simply trust that it is still ticking. The wood is the same kind of trust. The poem names no owl, no moth, no fox. Judging by that absence, the reader is meant to supply the creatures, and the activity stays a general, mechanical hum, like gears turning out of sight.
The word doing the most work is "business". It makes the wood sound like a workplace with a night shift, full of errands, appointments and small transactions. It also carries the old idiom of minding your own business, which suggests that whatever happens among the trees is none of ours. The tone is dry and slightly amused rather than awestruck, and the plain vocabulary supports that. Almost every word is short and everyday. "Business" is the longest in the poem, and it stands out the way a single bright coin would in a handful of pennies. "Full of" also works for both halves of the simile, since a clock is crammed with tiny moving parts and a wood with trunks, roots and unseen lives.
The sound of the lines helps too. There is no rhyme and no regular metre, but the rhythm is carefully varied. The first line is short and heavy. "Night wood" puts two strong beats side by side, which slows the line down, and the compound itself is telling. Where we might expect "the wood at night," the poem turns night into a property of the wood, as if after dark it becomes a different place. The second line hurries, and its run of s sounds ("is as full of business") has a whispering, ticking quality. The third line is the longest. It gives us one hard click in "clock," then loosens into soft vowels and finishes on "asleep," a word that sounds like what it means. The sentence runs out the way consciousness does. There is no full stop either, so the poem stops without ending, and the wood goes on.
The last clause is also slightly ambiguous. "When I am asleep" can attach to the clock alone or to the whole comparison, so it isn't clear whether the clock is busy while the speaker sleeps, or the wood is, or both. The ambiguity is useful, because it blurs the two images into one. The title adds to the effect. "Nocturnal" usually describes creatures that are active at night, and here the wood is the nocturnal thing, so the speaker, who is asleep, becomes the odd one out. The word also names an old instrument for telling the time at night by the stars, so a clock is hiding inside the title as well. Whether or not that was intended, it fits.
What makes the poem significant is how much it does with so little. It moves the human being out of the centre without any gloom. The speaker doesn't sound shut out by the night wood's activity, and may even be comforted by it, the way a ticking clock reassures a sleeper. The poem's argument is that things matter and go on whether or not we are conscious of them. It delivers that in a single image, and once you have read it, a dark wood and a quiet room are both a little harder to think of as empty.