The first line of the poem already clues us into the fact that this is a poem about nature and landscape. “Land” is in that first line, after all. This line is repeated three more times (lines 6, 7, and 12). From this line, it’s clear that this is a poem about the beauty of nature.
The voice of thunder Within the dark cloud (3-4)
Here we’re getting an image of the awesome power of nature and of nature’s voice. Thunder is a pretty scary noise, and so is the dark cloud, but it’s also beautiful. It’s one of the things that lends nature its beauty.
The voice of the grasshopper Among the plants (9-10)
While thunder comes from the clouds, the voice of the grasshopper comes from the ground, from among plants. This image is giving us a sense of the fact that even the small voices of nature—in this case, those of insects—contribute to the beauty of nature.