Within the essay "Nature," Emerson utilizes parallel structure in asserting, "The flowers, the animals, the mountains, reflected the wisdom of his best hour, as much as they had delighted the simplicity of his childhood" to assert that nature's appeal to man does not end with one's childhood; in fact, its resonance in our lives amplifies in our most profound adult thinking.

Emerson employs the rhetorical device of concession when he acknowledges "Miller owns this field, Locke that, and Manning the woodland beyond. But none of them owns the landscape."  His point is that nature is a construct that supersedes any artificial incremental measure that mankind can come up with to try to lay claim to it.

Another rhetorical device Emerson makes use of is a claim of fact; in his argument he posits that "The greatest delight which the fields and woods minister, is the suggestion of an occult relation between man and the vegetable."  Emerson believes that there is a secret communication that exists between man and nature seen as "They nod to me, and I to them."  

Emerson makes a claim of value in stating, "Yet it is certain that the power to produce this delight, does not reside in nature, but in man, or in a harmony of both" to get across his idea that all men strive for happiness, and that it can only be found when man is in accord with nature.

Because the essay is meant to be persuasive in that it communicates Emerson's argument about the relationship between man and nature, his style utilizes appeals to ethos, pathos, and logos.  Despite the unconventionality of his position, he uses the formal structure of argument in making claims of fact and value while including techniques of poetry, such as metaphor. Emerson stops short of claims of policy, since his argument is not meant to result in anything other than a change in the way people think about nature.

In the very beginning, Emerson personifies Nature:

Nature says, -- he is my creature, and maugre all his impertinent griefs, he shall be glad with me.

This connects humanity with nature as if we exist as equals, as if we were dependent on one another.

He uses rhetorical questions to influence the reader.

Why should not we also enjoy an original relation to the universe? Why should not we have a poetry and philosophy of insight and not of tradition, and a religion by revelation to us, and not the history of theirs?

These questions challenge us and encourage us to liken ourselves to generations of the past.

He uses oxymoron or great paradox:

I am glad to the brink of fear.

Fear doesn't make us glad or vice versa. But when in Nature, I believe he is expressing that the ultimate benefit of being there is experiencing emotion at it's greatest extremes.

He uses simile and metaphor:

In the woods too, a man casts off his years, as the snake his slough, and at what period soever of life, is always a child. In the woods, is perpetual youth.

Comparisons like these are important because when readers can relate to things, they have a greater ability to grasp what a writer is saying.

Much of the above is in reference to your question about literary elements. In terms of style, he fits the style of an essay, but he uses a first person point of view which doesn't always happen in essays.