A fire burned on Tuesday morning across four acres of Roy’s Redwoods, a 292-acre preserve in Marin’s Open Space District just east of Nicasio Valley Road and home to home of the county’s oldest redwood trees. Fire officials say evidence indicates that humans started the fire, although it is not clear whether it was accidental or intentional. No injuries have been reported, and an investigation is ongoing. Mike Giannini, the battalion chief for the county’s…