COLORADO — “We have an epidemic of trees in Colorado,” said Stefan Reinold, a forester with Boulder County’s Parks and Open Space department. …The resulting abundance of densely packed pines and firs fuels huge blazes. In response, the federal government has committed nearly $5 billion to thinning forests on about 50 million Western acres over the next 10 years. Although this can be accomplished with prescribed burns, the risk of controlled fires getting out of hand has foresters embracing another solution: selectively sawing trees, then stripping the limbs from their trunks and collecting the debris. The challenge now is what to do with all those piles of sticks, which create fire hazards of their own. Some environmental scientists believe they have an answer: mushrooms. Fungus has an uncommon knack for transformation. Give it garbage, plastic, even corpses, and it will convert them all into something else — for instance, nutrient-rich soil.