Lumber is declining in America because the environazis have imposed sustainable development on us. It has nothing to do with tariffs and everything to do with environmental regulation and destruction of property rights.
In Santa Cruz county CA, it costs thousands of dollars to produce a report that is at least a thousand pages long, outlining your INTENT to harvest timber. Not a harvesting plan, an INTENT to harvest. This kind of crap destroys the property owners right to get economic value from his property, and gives the state ownership of the property-- the only privilege many timber owners have in CA is the right to pay TAXES.
(The predictable response by the U.S., of course, was to raise the tariff even higher -- but that only made things worse!)
More importantly, the improvements in productivity at Canadian mills made U.S. producers utterly uncompetitive in cases where the tariff doesn't apply -- like in export markets in Asia.
Your point about Santa Cruz County may be a valid one, but let me ask you this . . . your comment could just as easily apply to a manufacturing facility as to a forest, so what makes you think anything would be different in the manufacturing sector if the U.S. were to impose a tariff on Chinese imports?