see root barrier and tree protection zone barrier.

Merriam-Webster Online Dictionary
barrier (noun)
a) something material that blocks or is intended to block passage - highway barriers a barrier contraceptive
b) a natural formation or structure that prevents or hinders movement or action - geographic barriers to species dissemination barrier beaches drugs that cross the placental barrier
often capitalized a medieval war game in which combatants fight on foot with a fence or railing between them
something immaterial that impedes or separates - obstacle behavioral barriers trade barriers
barrier (Wikipedia)

A barrier or barricade is a physical structure which blocks or impedes something.

Barrier may also refer to:

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