The Secretary of Agriculture and the Secretary of the Interior are further severally authorized, whenever in their respective judgments the maintenance of a stable community or communities is primarily dependent upon the sale of timber or other forest products from federally owned or administered forest land and such maintenance cannot effectively be secured by following the usual procedures in selling such timber or other forest products, to establish by formal declaration for the purpose of maintaining the stability of such community or communities a sustained-yield unit consisting of forest land under the jurisdiction of the Secretary establishing such unit, to determine and define the boundaries of the community or communities for whose benefit such unit is created, and to sell, subject to such conditions and requirements as the Secretary believes necessary, federally owned or administered timber and other forest products from such unit without competitive bidding at prices not less than their appraised values, to responsible purchasers within such community or communities.