Fully-decayed material from the forest can be good for future generations of plants.  But before it can break down, it can also be a fire hazard. 

Lisa Herron with the U.S. Forest Service says burning downed trees and underbrush can protect the forest from fire and yield other benefits, "When woody material is burned, it does send nutrients back into the soil. Some species even require ash and those nutrients that it produces to regenerate"

Herron recommends campers call or check the forest service website before setting out for the Tahoe Basin to avoid getting smoked out.