This is not actually about nature it’s meaning nothing good can stay. In the outsiders this poem is used. When Johnny dies he says stay gold to Ponyboy meaning stay good.
The line that would be best described as an example of trochee would be "<span> Why so pale and wan, fond Lover?" In addition, a trochee is a poetic meter wherein the line usually starts with a stressed syllable and eventually followed by an unstressed syllable. This metrical foot is commonly used in classic poems.</span>
Bold best described the tone.