By Steve Olafson

OKLAHOMA CITY (Reuters) - A former state forest ranger who set dozens of wildfires has been sentenced to 10 years in prison and must help make a training video to help others spot the triggers that lead firefighters to commit arson, a prosecutor said Friday.

Mike Malenski, 39, pleaded guilty to arson and endangering human life for a series of fires that destroyed thousands of acres in a wildlife management area of northeast Oklahoma in 2010 and 2011.

A ranger with the Oklahoma Forestry Service for seven years, Malenski faced 56 counts of arson when he pleaded guilty and was sentenced on Thursday in Cherokee County.

"He apologized for it," assistant prosecutor B.J. Baker said.

Malenski also was ordered to pay $37,000 restitution to compensate volunteer fire departments for their expenses in fighting the arson fires, Baker said.

He will help make a video to assist firefighters trying to understand why colleagues commit arson and the "triggers" that precede the behavior, Baker said.

After volunteer firefighters raised suspicion about Malenski, investigators placed a global positioning system on his vehicle to track his movements.

When confronted, Malenski admitted he set the blazes, some of which burned up to 1,300 acres.

(Editing by Greg McCune and Stacey Joyce)