Older book civilization lives in the trees

[abbeyinc]

Trying to remember the name of a book, might have been a series, that I read in the 80's. Juvenile fiction.

The main parts I remember is that the people lived entirely in the trees and the it was very bad to go to the ground. It seems as if the main character ended up on the ground and discovered something important.

Not much I know but that is all I remember.

[abbeyinc]

I have been trying to remember any details of this book for weeks and then, out of nowhere, the title just came to me:

Below the Root

Thanks to anyone who might have puzzled over this for me.