To reach the heart and spirit of a human, the spirit guide may take the form of anything that is a part of that person's worldview. Light guides may take any form, color and name. They can be anything you'd want them to be. They come to you in a form you are able to embrace. They are spirit beings, too.
Nature spirits heal and protect the Earth and the nature.
You could say they work as guardian angels. You should show your respect for these beings when you connect with them. Animals and plants are living beings with spirit guides to lead and protect them. Maybe you know how it feels to sit under a beautiful tree and get energy and power from that tree. It is the spirit of the tree that's giving you a gift of great love.