72 Pa. Stat. § 5581
In consideration of the public benefit to be derived from the retention of forest or timber trees, the owner or owners of land in this commonwealth, having on it forest or timber trees averaging not fewer than fifty trees to the acre, each of said trees to measure at least eight inches in diameter, at a height six feet above the surface of the ground, with no portion of the said land absolutely cleared of the said trees, shall, upon filing with the assessor of their respective townships or districts, annually, an affidavit made by said owner or owners, or by some one in his, her or their behalf, upon blanks to be provided by the county commissioners of the respective counties, and by them to be furnished to the assessors for the purposes herein intended, setting forth the number of acres of timber land within the requirements of this act, be entitled to receive annually, during the period that the said trees are maintained in good condition upon the said land, a rebate equal to eighty per centum of all taxes, local and county, annually assessed and paid upon said lands, or so much of the eighty per centum as shall not exceed in all the sum of forty-five cents per acre; the said rebate to be deducted from said taxes pro rata, and receipted for by the respective tax collectors or county treasurer: Provided, however, That no one property owner shall be entitled to receive said rebate on more than fifty acres.
72 P.S. § 5581