PORTLAND, Ore. (AP) — The father and son of a prominent Oregon ranching family plan to surrender Monday to serve more time in prison for setting fires that spread to government lands they leased as cattle rangeland.

Seventy-three-year-old Dwight Hammond and 46-year-old Steven Hammond say they lit the fires in 2001 and 2006 to reduce the growth of invasive plants and protect their property from wildfires. The two were convicted three years ago and served time, but a judge ruled the terms were too short. Federal lawyers prosecuted the ranchers under an anti-terrorism law that they say required a five-year minimum sentence.

The decision to again imprison the Hammonds has generated controversy in a rural part of the state. It's also playing into a long-simmering conflict between ranchers and the U.S. government over the use of federal land.