(Corvallis, OR) -- A new study out of Oregon State University shows forest thinning helps older trees and makes forests stronger. Researchers studied a forest in Oregon's Blue Mountains. It found thinning trees made older trees more robust. It also strengthened the forest against disease and devastating wildfires. The benefits of thinning take three to four years to happen. It also allows grasses and shrubs to grow that are less likely to cause a major fire.