Accomplishing Forest Restoration with Biomass Harvesting Methods

Eagle Lake Ranger District
Lassen National Forest

Fuel Reduction Projects

Defensible Fuel Profile Zones (DFPZs)

Since the initiation of the HFQLG Bill in 1999, the Eagle Lake RD had been working on the establishment of a comprehensive fuel break system called defensible fuel profile zones (DFPZs). The District has been completing 3,000 to 5,000 acres of this mechanical, biomass DFPZ thinning per year since 1999. The following photographs and information are reflective of two examples of mechanical DFPZ thinning.

Eastside Pine DFPZ

B1

The stand in the photograph above represents approximately 805 trees per acre in a typical eastside pine type, prior to implementation of the DFPZ prescription and biomass mechanical thinning. Most of the trees in the stand are less than 12 inches in diameter.

B2

This is the same photo point after thinning. The mechanical biomass thinning removed most of the ladder fuels in the stand and decreased the average trees per acre from 805 to 107. The stand is also "trending" toward a stand structure that is more similar to pre-settlement conditions.

This DFPZ was approximately 393 acres in size and was implemented with a timber sale contract. The contractor was required to remove all undesignated (unpainted trees) from 3 inches dbh to 29.9 inches dbh. Approximately 45 green tons of biomass per acre was removed in the thinning which generated an average of $204.37 in revenues per acre.

Mixed Conifer DFPZ

B3

This photograph represents an older, eastside mixed conifer stand on the District prior to DFPZ implementation. The stand structure is the result of over 100 years of fire suppression. The stand consist of two age classes of trees; the larger, scattered, older trees that existed prior to fire suppression, and the denser, smaller trees that are the result of fire suppression from the mid-1800s.

There are approximately 297 trees per acre in this photograph prior to thinning. The quadratic mean diameter (QMD) prior to thinning was 15.7 inches.

B4

This DFPZ project is approximately 646 acres in size and was implemented with a timber sale. The biomass harvest removed approximately 50 green tons per acre with the thinning and generated an average of $441 per acre in revenues.

After the thinning, the average trees per acre were reduced to 68 with an average stand diameter or QMD of 26.1 inches. The result of the thinning was removal of the ladder fuels and "trending" the stand toward pre-settlement structure.

Soil Moisture

The biomass thinnings for DFPZs have proven very effective at reducing ladder fuels within treated stands and has improved the health and vigor of the residual conifers. This increase in health and vigor is evident by monitoring the plant available moisture between treated (thinned) and untreated portions of a stand.

SM1

Underburning a DFPZ

Most mechanically thinned stands on the District are treated with an understory prescribed fire within five years of the DFPZ thinning.

UB1 - Pre-Burn: 2001

UB2 - Post-Burn: 2002

The Swains DFPZ was thinned in 1998 with the Poison Small Log Timber Sale which treated 965 acres and produced 19 green tons per acre of biomass, and generated $52.09 per acre in revenues. The underburn occurred in the fall of 2001.

As evident in the photographs, the first growing season after the underburn the amount of native grasses increased significantly, while brush composition decreased. The shift from a predominantly brush understory to more grass is what is expected in a fire prone ecosystem on Eagle Lake. The shift in vegetative species diversity increases wildlife habitat values.