VOCABULARY - O
Oak Savanna - a rare ecosystem that is mixture of oak trees and grasses and an intermediate between a prairie and oak woodlands.
Old Growth Forest - a forest significantly past the age of maturity of its dominant species. Usually characterized by well-developed structure, many snags, dead wood on the ground; a late successional forest type for the area; sometimes refers to undisturbed or never harvested areas.
Omnivore - an organism which gets its food energy from both plant and animal material.
Opposite Branching - a branching pattern where side branches, leaves, and leaf scars grow directly across the stem from each other.
Outwash - glacial material, usually sand or gravel, which is deposited by water melting off glaciers.
Overstory - the uppermost trees in a forest.
Overtopped - trees with crowns entirely below other trees around them. They receive no direct sunlight from above or the sides.