Timber Supply Stability Act

Timber Supply Stability Act - Directs the Secretary of Agriculture to determine the number of acres in each national forest that, as of January 1, 1988, were administered through the Chief of the Forest Service (excluding any lands not suited for timber production). Names such acreage the timber base for that national forest and the aggregate timber base for all national forests the National Forest System timber base. Requires the Secretary to report to the Congress annually on such timber base.

Declares that it is the policy of the Congress that any diminution of the timber base of a national forest be offset by the acquisition of additional timber lands for that national forest.

Authorizes any State to impose an export tax of 25 percent on unprocessed logs as of the time of their removal.

Establishes the Timber Base Acquisition Trust Fund, consisting of amounts equivalent to such export taxes received in the Treasury, plus certain appropriations from the Land and Water Conservation Fund. Requires investment of a portion of the Trust Fund in interest-bearing obligations of the United States.

Makes available to a State for a five-year period for timber land acquisition an amount equal to 25 percent of the export taxes raised in that State in a fiscal year. Conditions the availability of such funds on the State's agreement that all timber harvested from acquired lands shall be processed in the United States.

Makes available to a State that has adopted an export tax any amounts remaining in the Trust Fund for a fiscal year after all 25-percent payments. Restricts the use of such additional funds to the acquisition on a willing seller basis of timber lands for national forests. Permits the Secretary to use, also for timber land acquisition in that State, any funds remaining to a State's allocation after all 25-percent, and any additional payments.

Sets forth criteria and guidelines for the acquisition by the Secretary of replacement timber lands for a national forest.