Cal. Rev. & Tax. Code § 38109

“Immediate harvest value” means the amount that each species or subclassification of timber would sell for on the stump at a voluntary sale made in the ordinary course of business for purposes of immediate harvest. Such immediate harvest values shall be expressed in terms of amount to the nearest dollar per thousand board feet, net Scribner Decimal C log rule, or other unit of measure chosen by the board, and shall be determined in a manner which makes reasonable and adequate allowances for age, size, quality, costs of removal, accessibility to point of conversion, market conditions and all other relevant factors as determined by the board.

For the purposes of this section, the immediate harvest value of Christmas trees shall be the sale price of the Christmas trees in quantities of 100 trees or more in the market area nearest to the place where the trees are cut.

Prior to December 31, 1976, and periodically thereafter as determined by the board, the board in consultation with the Timber Advisory Committee and with the California Division of Forestry and after public hearings, shall adopt rules and regulations establishing a standard unit of measure and establishing conversion factors which convert prevalent units of measure in use in California to Scribner Decimal C log rule or other unit of measure chosen as a standard.