If the taxpayer so elects on his return for a taxable year, the cutting of timber (for sale or for use in the taxpayer’s trade or business) during such year by the taxpayer who owns, or has a contract right to cut, such timber (providing he has owned such timber or has held such contract right for a period of more than 1 year) shall be considered as a sale or exchange of such timber cut during such year. If such election has been made, gain or loss to the taxpayer shall be recognized in an amount equal to the difference between the fair market value of such timber, and the adjusted basis for depletion of such timber in the hands of the taxpayer. Such fair market value shall be the fair market value as of the first day of the taxable year in which such timber is cut, and shall thereafter be considered as the cost of such cut timber to the taxpayer for all purposes for which such cost is a necessary factor. If a taxpayer makes an election under this subsection, such election shall apply with respect to all timber which is owned by the taxpayer or which the taxpayer has a contract right to cut and shall be binding on the taxpayer for the taxable year for which the election is made and for all subsequent years, unless the Secretary, on showing of undue hardship, permits the taxpayer to revoke his election; such revocation, however, shall preclude any further elections under this subsection except with the consent of the Secretary. For purposes of this subsection and subsection (b), the term “timber” includes evergreen trees which are more than 6 years old at the time severed from the roots and are sold for ornamental purposes.