Eastern Oregon forest restoration efforts hampered by diameter limits on tree cutting March 9, 2021 CORVALLIS, Ore. – A quarter-century-old harvesting restriction intended to last one year has served as an obstacle to returning eastern Oregon national forests to the healthier, more fire-resilient conditions they embodied in the late 1800s, research by the Oregon State University College of Forestry shows. The findings, published in Ecosphere, are both important and timely because the U.S. Forest Service recently revised what has widely become known as the “21-inch rule” – a prohibition against cutting trees greater than 21 inches in diameter at breast height on Forest Service land in eastern Oregon.