For each of the calendar years 1969 through 1973, inclusive, not more than 350 million board feet, in the aggregate, of unprocessed timber may be sold for export from the United States from Federal lands located west of the 100th meridian.
After public hearing and a finding by the appropriate Secretary of the department administering Federal lands referred to in subsection (a) that specific quantities and species of unprocessed timber are surplus to the needs of domestic users and processors, such quantities and species may be designated by the said Secretary as available for export from the United States in addition to that quantity stated in subsection (a).
The Secretaries of the departments administering lands referred to in subsection (a) may issue rules and regulations to carry out the purposes of this section, including the prevention of substitution of timber restricted from export by this section for exported non-Federal timber.
In issuing rules and regulations pursuant to subsection (c), the appropriate Secretaries may include therein provisions authorizing the said Secretaries, in their discretion, to exclude from the limitations imposed by this section sales having an appraised value of less than $2,000.