Personification "Yonder beeches from their barks" are claiming that their home has large trees with smooth gray barks.
Theme & Explanation
The "thunder o'er my head and now the distance dies" claims how to thunder is so loud that it feels like it's right next to you. Also the "distance dies" mean's how the thunder is fading away.
Textual Evidence of the Theme
"With groves of evergreen" claims to say that the group of trees will have bright and beautiful green for ever.
The theme of this poem is how she describes her home and how she is leaving or moving away and also showing all the beautiful parts of her home.
In the text it stated how it describes the poem theme in most of the stanzas. The two stanzas that stand out the most were stanzas 4 "For yonder garden, fair and wide, with graves of evergreen" and stanza 5 "With grey walls compassed round, where knotted grass neglected lies"