The Chief, Forest Service, shall establish minimum stumpage rates, i.e., “base rates,” for species and products on individual National Forests, or groups of National Forests. Timber shall be sold for appraised value or minimum stumpage rates, whichever is higher. No timber may be sold or cut under timber sale contracts for less than minimum stumpage rates except to provide for the removal of insect-infested, diseased, dead or distressed timber or in accordance with contract provisions specifically providing for catastrophically-affected timber and incidental amounts of material not meeting utilization standards of the timber sale contract. For any timber sale offering where deposits are to be required for reforestation under the Act of June 9, 1930, as amended (46 Stat. 527; 16 U.S.C. 576-576b) which exceed the value of the established minimum stumpage rates, the minimum rates may be increased by the approving officer as necessary to the amount of such required reforestation deposits and a minimum deposit to the Treasury. Minimum rates in timber sale contracts will not be set higher than established minimum rates for purposes other than assuring adequate funds for reforestation.