Fire and Fuels Management

Forest Service employee uses a fire hose to spray water on a prescibed fire. Photo Credit: Rex Norman, USFS.

Prescribed fire is an important tool for ecosystem restoration and management. For more information, visit our Current Prescribed Fire web page for locations and maps.

Lake Tahoe Basin Multi-Jurisdictional Fuel Reduction and Wildfire Prevention Plan

Multi-Jurisdictional Fuel Reduction and Wildfire Prevention Strategy - August 2014
(PDF 5,475 KB)

Background

Before the logging and settlement that began with the Comstock era mining, frequent fires shaped the Lake Tahoe Basin forest. Tree ring studies show that fires burned every five to 20 years on average. These lower intensity fires helped create a complex mosaic pattern of towering old-growth conifers and diverse under story plants, thus helping to maintain a healthy ecological balance in the Tahoe Basin. Recognizing that agencies will not be able to reintroduce fire across the entire Lake Tahoe landscape, reintroducing fire into the Lake Tahoe environment will partially restore the ecosystem to its pre-settlement condition and function.

In the absence of natural fire, a thick layer of downed fuel and smaller trees have accumulated in Lake Tahoe's forests, creating a severe fire risk. The Lake Tahoe Basin Management Unit (LTBMU) and other agencies are implementing a program of prescribed fire underburns that are scientifically appropriate for fire adapted ecosystems.

Although slash pile burning is not a restoration tool, it is an efficient fuel reduction treatment method in areas not suitable for underburns. For safety considerations near residential areas, slash pile burning is most often the best treatment method following thinning treatments in overly dense stands that would burn too intensely in an underburn causing unacceptable levels of tree scorch and mortality.

Current Situation

Since 1997, over 2,000 acres of landscape underburns and over 8,000 acres of prescribed pile burning has been implemented on the LTBMU. In these areas, surface fuels have been reduced and smaller live trees thinned, creating a zone where a damaging crown fire is less likely which provides a safer environment for firefighters.

Increasing the annual number of acres treated with prescribed fire will challenge our future capacity. Despite refinements and improvements in notification and public education, smoke intrusion into nearby neighborhoods will likely increase. Increasing the number of days suitable for burning means more summer burning, which is not likely to dramatically increase acreage accomplishments.

Pile Burning in the Lake Tahoe Basin

Why piles?

The piles of brush, limbs and tree boles (stems) that one sees all over the LTBMU have been generated from Hazardous Fuels Reduction and Forest Health work being done by Forest Service crews and contractors. The work they are completing is thinning the forest and piling the heavy accumulation of surface fuels. These surface fuels have accumulated over the years because of the exclusion of fire from the Lake Tahoe Ecosystem. In the mid to lower elevations of the Lake Tahoe Basin, fire historically burned in low intensity fires every 8-15 years consuming these fuels. Now, these fuels exist in enormous quantities in many areas. In an effort to reduce the threat of wildfire the Forest Service is using the best means at its disposal to remove these fuels and modifying the forest condition.

When will the piles be burned?

The Forest Service must allow the piles to "cure" or dry out to allow for the effective consumption of the fuels. Normally, this takes approximately 18 months because of the size of some of the material thinned. Once the Forest Service Fuels and Fire Specialists have determined the piles are sufficiently dry, they will be burned by trained fire crews on permissive "burn days". Permissive burn days are determined by the Air Quality Regulators and based on current and forecasted weather conditions. The Forest Service staff will burn throughout the year insuring due caution is taken to insure safety. These measures include having sufficient personnel on site and water available to keep the burning pile under control and within the prescribed conditions in the plan approving the burning.

Effects of the Burning

Smoke

All fires produce smoke. The amount of smoke that will be produced is dependent on the moisture of the wood burning. In an effort to minimize smoke, the Forest Service will allow the piles to dry out or "cure" for approximately 18 months. Other factors that effect the amount of smoke that may affect residents is the weather conditions. Ideally, a moderate wind with an unstable air mass in the area is ideal. Occasionally a more stable air and lighter winds will increase smoke impacts as is periodically experienced. If this occurs, the Forest Service crews will change operations to put out all the piles burning. Impacts from pile burning smoke are short term and less intense than that of a wildfire.

Scorch

Scorch on the trees can be seen after the burning operations as the browning or die-back of the lower limbs or on occasion the entire tree. Generally speaking, the less fire resistant and less desirable white fir trees are the most easily scorched. The Jeffery Pine is far more resistant to fire effects. When the Forest Service conducts burning operations, we make every effort to minimize the scorch to the remaining trees. Unfortunately, scorch will happen, and fortunately it is a short term condition. As we discussed previously, the forest stands in the Lake Tahoe Basin have not had natural fire for over 100 years. As a result, the lower limbs of the trees have continued to grow and not been burned away naturally. The burning of the piles begins to emulate the natural process of "raising" the crown of the trees higher off the ground and making the forest stands better able to resist a fire in the future. It is desirable to have the lowest limbs of the trees 15-20 feet above the ground. Within two years the vast majority of the scorched needles will have fallen off the tree, leaving a more fire resistant stand.

Small isolated areas of tree crown scorch resulting in tree death are anticipated as pile burning is implemented. Where tree crown scorch is excessive, Forest Service crews will identify and fall the affected trees, creating new slash piles that will subsequently be burned.

Bones

Occasionally, the piles do not burn up completely, leaving areas of charred logs. To reduce the impact of this, Forest Service crews will either re-burn the accumulation of charred pieces, or spread them through the stand to resemble what the forest floor would look like after a natural burn and to provide woody material to decompose providing nutrients and an environment for microbes and organisms.

Benefit of the burning

The benefit of burning these piles has been touched on previously. Natural fire has been excluded from the Lake Tahoe Basin forest stands for over 100 years. These natural fires burned at a low intensity and with a frequency of every 8-15 years, consuming limbs, needles, cones, debris, small trees and brush. They also resulted in the lower limbs of the remaining trees being burned to a height of 15-20 feet off the ground. All this led to a forest stand that was resistant to a crown fire. The activity of pile burning is the result of Forest Service crews and contractors thinning small diameter trees and picking up limbs and debris that would have been burned up during a naturally occurring fire. While pile burning does not have the benefit of large area burning, as a natural fire would, it does rid the forest of the unnatural accumulations of the surface fuels, burns the lower limbs effectively raising the height of the crowns. If the fire from the piles is allowed by the Burn Plan to "creep around" (burn through the duff and litter surrounding the pile for a short distance) there is the increased benefit of consumption and removal of just that much more fuels that potentially could feed a wildfire.

Future

Pile burning in the Lake Tahoe Basin will continue. It is but one "tool" in the Forest Service's "tool box" to effectively reduce the threat from wildfire and manage the forest areas for a more fire resistant condition. As the biomass markets continue to develop and technological advances are made for removal, there will be a few less acres burned in favor of biomass utilization. Unfortunately, today, biomass utilization requires reasonable road access and slope less than 30%. Only about 30% of the National Forest lands requiring treatment are available for biomass utilization. The remaining acreage will still need treatment of some degree. Today, the only means to dispose of the material is by hand piling and burning the thinned trees and 100 years of accumulated limbs, litter, and wood. The Forest Service will strive to minimize the impacts from smoke to the Lake Tahoe residents. Unfortunately, we cannot guarantee no impacts. Fortunately, the smoke impacts from pile burning are short lived and are considerably less that the impacts from the wildfire that is likely to occur if no work is done.