Interfor Corp. says it will reduce lumber production by at least eight per cent of capacity in the first quarter as market uncertainty affects demand.    The Burnaby, B.C.-based forestry company says the move amounts to at least 100 million board feet.    It says it expects to resume its normal production schedule starting in April but will monitor market conditions and adjust plans accordingly.    The company says the production cuts are likely to come from areas other than its U.S. South operations.     ...