ARLINGTON, Washington — About 13 miles from town, nature stood still as a forester for the state Department of Natural Resources measured the age of a Douglas fir near a timber sale site known as Stilly Revisited. …At Stilly Revisited, forest activists are concerned about protecting old growth trees and — in a valley still healing from the deadly Oso mudslide in 2014 — preventing future slides. They also question how Stilly Revisited and three other pending timber sales in Snohomish County meet a DNR goal to conserve 10% to 15% of old growth and structurally complex forests in the department’s Northwest Washington region. …But the DNR’s crew of geologists, foresters and timber sale managers are tasked with addressing individual harvests. The state’s Board of Natural Resources is responsible for broader policies. DNR is “conservative” about harvesting trees on public lands, said DNR Cascade District Manager Mark Arneson.