Cal. RTC § 423.5

When valuing open-space land which is enforceably restricted and used for the production of timber for commercial purposes, the county assessor shall not consider sales data on lands, whether or not enforceably restricted, but shall determine the value of such timberland to be the present worth of the income which the future harvest of timber crops from the land and the income from other allowed compatible uses can reasonably be expected to yield under prudent management. The value of timberland pursuant to this section shall be determined in accordance with rules and regulations issued by the board. In determining the value of timberland pursuant to this section, the board and the county assessor shall use the capitalization rate derived pursuant to subdivision (b) of Section 423. The ratio prescribed in Section 401 shall be applied to the value of the land determined in accordance with this section to obtain its assessed value.

For the purposes of this section, the income of each acre of land shall be presumed to be no less than two dollars ($2), and the present worth of this income shall not be reduced by the value of any exempt timber on the land.

There shall be a rebuttable presumption that “prudent management” does not include use of the land for recreational use, as defined in subdivision (n) of Section 51201 of the Government Code, unless the land is actually devoted to such use.