The U.S. Forest Service is using airplanes to spread mulch over the steepest slopes burned during the Angora fire, in an attempt to reduce runoff into Lake Tahoe.
The sticky mulch, made from 650 of the 3,100 acres scorched in the fire, provides a protective coating to cover areas that are most vulnerable to erosion.
It is part of a $2.9 million effort to address urgent post-fire needs following the blaze that destroyed about 250 homes in late June and early July.
The fire also ruined about 7 percent of the watershed of the upper Truckee River, which flows into Lake Tahoe.
But the delicate mulch "can easily be damaged by people walking on it," said Forest Service spokesman Rex Norman, prompting officials to increase patrols in the treated areas and ask hikers and bikers to avoid trails until at least spring.
Footsteps could make the material flake off and blow away, or lift up from the soil surface enough that water can flow beneath it, reducing its ability to fight erosion, Norman said.
Researchers who had hoped to enter the area to study nutrient movement in the fire-damaged soils are disappointed.
Geoff Schladow, director of the University of California, Davis' Tahoe Environmental Research Center, said fires are likely to recur around the lake and could put a great deal of stress on the environment there, so it's vital to study their aftermath.
"This was the silver lining to a particularly dark cloud - that we could actually learn something from the fire," said Schladow, who had hoped to conduct five years of research into issues such as the movement of nitrogen and phosphorous.