(Corvallis, OR)  --  Oregon State University says it is revamping its forest management plan after several ancient trees were cut down in the school's research forest.  The College of Forestry cut down about 15 acres of old trees for timber, and later learned that some of the trees were 260-years old.  One was estimated to be 420 years old.  College officials say the trees were listed in a harvest section of the forest management plan, about 27 years ago.