Here are books, DVD's and such, that will give you understanding of trees and treatments. In Florida when my questions extended beyond the information provided by the certification program of LMA I was directed to this stuff. In 1991 I started dissecting trees with the author and continued until he died a year and a half ago. This is great stuff. You can request this stuff at your local library and they should be able to get them. My business started doing MODERN ARBORICULTURE in 1991 when the book was released.
Also here is a collection of some of the articles he wrote.
His literature along with dissecting workshops has given me an understanding of trees and their associates and treatments.
I would suggest MODERN ARBORICULTURE and TREE PRUNING - A worldwide photo guide for starters. A NEW TREE BIOLOGY is also a great book about trees.