If the focus of the question is to find poems with the theme of harmony in nature, I think that one of the best places to look would be in the poems of William Wordsworth. The poetry of Wordsworth affirms the idea that there is a way for individuals to find harmony with the natural world. The means through which this is possible is to leap from what is into a world of what can be. This is best seen in Wordsworth's "I Wandered Lonely as a Cloud." The premise of the poem is how the speaker, presumably Wordsworth, feels when he beholds the natural setting of a field of daffodils. In linking his own sense of being with the natural experience, there is a theme of harmony with the world. The ending of the poem speaks to the leap one needs to take in order to find this mode of harmonization:
For oft when on my couch I lie
In vacant or in pensive mood,
They flash upon that inward eye
Which is the bliss of solitude;
And then my heart with pleasure fills,
And dances with the daffodils.
Wordsworth suggests that there must be a "vacant or in pensive mood" that enables the leap to happen. This transformative power lies within "that inward eye" that Wordsworth sees as "the bliss of solitude." This is where harmony lies.
Harmony is realized when the individual is able to shift one's thinking into a capacity of what can be from what is. Wordsworth suggests that the individual must break themselves off from conformist society in order to find this reality. If individuals have this will and are able to "dance with the daffodils," the leap towards harmony is evident. The work of William Wordsworth is one realm where one can find the poetic means of harmonization between the individual and nature and the leaps needed to embrace it.
Thank you very much for your very helpful and kind answer, Mr. Kannan! I'm still wondering, though, whether if I could get acquainted with poems about harmony of(amongst) people. I know I am being rather annoying but would you kindly let me know some poems with the very theme, if you don't mind?