BILLINGS, Montana — The Biden administration is moving to conserve groves of old-growth trees on federal land by revising management plans for national forests and grasslands across the U.S. as climate change amplifies the threats they face from wildfires, insects and disease. Agriculture Sec. Tom Vilsack said the goal was to provide an “ecologically-driven” approach to older forests — an arena where logging interests have historically predominated. It would be the first nationwide amendment to U.S. Forest Service management plans in the agency’s 118-year history, he said. It follows longstanding calls from environmentalists to preserve older forests. …Biden’s administration appears to be aiming for a middle ground: It would sharply limit commercial timber harvests in old growth forests while allowing logging to continue on “mature forests” that have not yet reached old growth stage. But representatives of the timber industry and some members of Congress have been skeptical.