The term 'forest unit' refers to a unit of land that is covered by trees and other vegetation. An ACRE is a unit of area, equal to 4, 840 square yards or 43, 560 square feet, and a tree is a woody perennial plant typically having a single stem or trunk growing to a considerable height and bearing lateral branches at some distance from the ground. Together, these two terms form a unit of land that is covered by trees and other vegetation, and is measured in acres and trees.