There are some good chemistry articles regarding tree chemistry here for
those who like to read well written stuff.

Troubles in the Rhizosphere and A Touch of Chemistry to name two.

http://www.treedictionary.com/DICT2003/shigo

enjoy!

Sincerely,
John A. Keslick, Jr.
Consulting Forester & Tree Expert
www.treedictionary.com

http://home.ccil.org/~treeman/

Beware of so-called tree experts who do not understand tree biology.
Specifically people like Don Staples who claim logging and salvaging is in
the interest of forest health.
http://www.livingston.net/dstaples/forestry/staples.htm He flunked tree
anatomy.
Storms, fires, floods, earthquakes, and volcanic eruptions keep reminding us
that we are not the boss.