Cal. Public Resources Code § 4561

It is the purpose of this section to set forth resource conservation standards for timber operations, and to ensure that a cover of trees of commercial species, sufficient to utilize adequately the suitable and available growing space, is maintained or established after timber operations. To that end, the following resource conservation standards define minimum acceptable stocking, and an area covered by a timber harvesting plan shall be classified as acceptably stocked if either of the following conditions exist within five years after completion of timber operations: (a) The area contains an average point count of 300 per acre, except that in areas that the registered professional forester who prepares the timber harvesting plan has determined are site IV classification or lower, the minimum average point count shall be 150 per acre. Point count shall be computed as follows: (1) A countable tree that is not more than four inches in diameter at breast height to count as one. (2) A countable tree over 4 inches and not more than 12 inches in diameter at breast height to count as three. (3) A countable tree over 12 inches in diameter at breast height to count as six. (b) (1) The average residual basal area, measured in stems one inch or larger in diameter is at least 85 square feet per acre, except that in areas that the registered professional forester who prepares the timber harvesting plan has determined are site II classification or lower, the minimum average residual basal area shall be 50 square feet per acre. (2) The board, on a finding that it is in furtherance of the purposes of this chapter, may encourage selection, shelterwood, or other types of management of timber if consistent with the biological requirements of the tree species and may regulate the size and shape of areas in which even-age management of timber is utilized. (3) Rock outcroppings and other areas not normally bearing timber shall not be considered as requiring stocking and are exempt from the stocking provisions.