In section 2 of Song of Myself, what is meant by the line "Echoes, ripples, buzz'd whispers, love-root, silk thread, crotch and vine"?
In the first section, Whitman takes on the role of Everyman, a typical American working man, but he also represents himself as a sensuous poet. The one thing all humans have in common is their sexuality. The shifts in the different sections between body and soul illustrate the central theme of the endless renewal of life. When the individual dies, "life" goes on, but the individual can still triumph over death by accepting this knowledge and feeling at one with life.
In the second section to which you are referring, Whitman establishes the connections between individuals to other people, to nature, and to the whole universe. In the stanza just before the one you're referencing, he tells us that the air we breathe isn't like a perfume, but it reflects the air of nature that can be found beside a river in the woods, or basically anything in nature. He then continues with the effects of this air on him. "...My respiration and inspiration, the beating of my heart, the passing of blood and air through my lungs,..." makes this connection. It is an atmosphere that brings to life all of the senses of his breath, his smell, his touch, and his taste. Whitman makes the connection between nature and man and our physical bodies with our spiritual beings, which is the unity of our bodies and souls.