FEDERAL WAY, Wash.(Reuters) - Forest products giant Weyerhaeuser Co. said on Tuesday it will close a Canadian containerboard mill, cutting 140 jobs, in an effort to streamline its business and boost efficiency. The company, based in Federal Way, Washington, said it will close its Sturgeon Falls, Ontario, mill around Dec. 6, eliminating 100,000 tons of capacity. About six employees will stay on to operate the property's hydroelectric dam. Last month, Weyerhaeuser said third-quarter profits would fall below estimates due to low wood prices and U.S. import duties on Canadian softwood lumber. Shares of the company closed at $38.90 Monday on the New York Stock Exchange.