Southbound Highway 101 will be down to one lane each morning this weekend in northern Marin County as Caltrans trims elm trees along the road. The lane will be closed 5:30 to 9 a.m. Saturday and 5:30 to 9:30 a.m. Sunday between the Redwood Landfill interchange and the entrance to Olompali State Historic Park. Caltrans spokesman Robert Haus said in a statement that crews would be cutting dead and diseased tree limbs. Follow the Road Warrior on Twitter via @PDRoadWarrior