California Code, Public Resources Code - PRC § 4528

(a) “Basal area per acre” means the sum of the cross-sectional areas at breast height of the tree stems of commercial species per acre.

(b) “Countable tree” means a tree that can be used in calculating the degree of stocking under the following criteria:

(c) “Stocking” means a measure of the degree to which space is occupied by well-distributed countable trees.

(d) “Site classification” means the classification of productive potential of timberland into one of five classes by board regulation, consistent with normally accepted forestry practices.  Site I shall denote sites of highest productivity, site II and site III shall denote sites of intermediate productivity potential, and site IV and site V shall denote sites of lowest productivity potential.

(e) “Fuel break” means a strip of modified fuel to provide a line from which to work in the control of fire.

(f) “Stream” means a natural watercourse as designated by a solid line or dash and three dots symbol shown on the largest scale United States Geological Survey map most recently published.